diff --git a/src/ifcblenderexport/blenderbim/bim/__init__.py b/src/ifcblenderexport/blenderbim/bim/__init__.py
index 511fa5d248..196d6e1ad6 100644
--- a/src/ifcblenderexport/blenderbim/bim/__init__.py
+++ b/src/ifcblenderexport/blenderbim/bim/__init__.py
@@ -63,8 +63,6 @@ if bpy is not None:
         operator.SelectSweptSolidInnerCurves,
         operator.AssignSweptSolidExtrusion,
         operator.SelectSweptSolidExtrusion,
-        operator.AddQto,
-        operator.RemoveQto,
         operator.AddMaterialPset,
         operator.RemoveMaterialPset,
         operator.AddMaterialLayer,
@@ -159,7 +157,6 @@ if bpy is not None:
         operator.PropagateTextData,
         operator.ConvertLocalToGlobal,
         operator.ConvertGlobalToLocal,
-        operator.GuessQuantity,
         operator.ExecuteBIMTester,
         operator.BIMTesterPurge,
         operator.SelectIfcPatchInput,
@@ -270,7 +267,6 @@ if bpy is not None:
         ui.BIM_PT_material,
         ui.BIM_PT_presentation_layer_data,
         ui.BIM_PT_object_material,
-        ui.BIM_PT_object_qto,
         ui.BIM_PT_classification_references,
         ui.BIM_PT_documents,
         ui.BIM_PT_constraint_relations,
diff --git a/src/ifcblenderexport/blenderbim/bim/import_ifc.py b/src/ifcblenderexport/blenderbim/bim/import_ifc.py
index 5c202bc7da..7e9b061fd4 100644
--- a/src/ifcblenderexport/blenderbim/bim/import_ifc.py
+++ b/src/ifcblenderexport/blenderbim/bim/import_ifc.py
@@ -975,7 +975,6 @@ class IfcImporter:
         self.add_element_classifications(element, obj)
         self.add_element_document_relations(element, obj)
         self.add_opening_relation(element, obj)
-        self.add_product_definitions(element, obj)
         self.added_data[element.GlobalId] = obj
 
         if element.is_a("IfcOpeningElement"):
@@ -1355,15 +1354,6 @@ class IfcImporter:
         bpy.ops.mesh.normals_make_consistent(context_override)
         bpy.ops.object.editmode_toggle(context_override)
 
-    def add_product_definitions(self, element, obj):
-        if not hasattr(element, "IsDefinedBy") or not element.IsDefinedBy:
-            return
-        for definition in element.IsDefinedBy:
-            if not definition.is_a("IfcRelDefinesByProperties"):
-                continue
-            if definition.RelatingPropertyDefinition.is_a("IfcElementQuantity"):
-                self.add_qto(definition.RelatingPropertyDefinition, obj)
-
     def add_pset(self, pset, props):
         new_pset = props.psets.add()
         new_pset.name = pset.Name
@@ -1392,27 +1382,6 @@ class IfcImporter:
                     new_prop.name = prop.Name
                     new_prop.string_value = str(prop.NominalValue.wrappedValue)
 
-    def add_qto(self, qto, obj):
-        new_qto = obj.BIMObjectProperties.qtos.add()
-        new_qto.name = str(qto.Name)
-        qto_template = schema.ifc.psetqto.get_by_name(new_qto.name)
-        if qto_template:
-            for prop_name in (p.Name for p in qto_template.HasPropertyTemplates):
-                prop = new_qto.properties.add()
-                prop.name = prop_name
-        for prop in qto.Quantities:
-            if prop.is_a("IfcPhysicalSimpleQuantity"):
-                value = getattr(prop, "{}Value".format(prop.is_a()[len("IfcQuantity") :]))
-                if not value:
-                    continue
-                index = new_qto.properties.find(prop.Name)
-                if index >= 0:
-                    new_qto.properties[index].string_value = str(value)
-                else:
-                    new_prop = new_qto.properties.add()
-                    new_prop.name = prop.Name
-                    new_prop.string_value = str(value)
-
     def add_opening_relation(self, element, obj):
         if not element.is_a("IfcOpeningElement"):
             return
@@ -1708,7 +1677,6 @@ class IfcImporter:
 
         self.add_element_classifications(element, obj)
         self.add_element_document_relations(element, obj)
-        self.add_product_definitions(element, obj)
         self.aggregates[element.GlobalId] = obj
         self.aggregate_collections[rel_aggregate.id()] = collection
 
@@ -1769,7 +1737,6 @@ class IfcImporter:
         obj.matrix_world = self.get_element_matrix(element, mesh_name)
         self.add_element_classifications(element, obj)
         self.add_element_document_relations(element, obj)
-        self.add_product_definitions(element, obj)
         self.added_data[element.GlobalId] = obj
 
     def add_element_document_relations(self, element, obj):
diff --git a/src/ifcblenderexport/blenderbim/bim/module/cobie/__init__.py b/src/ifcblenderexport/blenderbim/bim/module/cobie/__init__.py
index 98091992a3..46ec55b5b6 100644
--- a/src/ifcblenderexport/blenderbim/bim/module/cobie/__init__.py
+++ b/src/ifcblenderexport/blenderbim/bim/module/cobie/__init__.py
@@ -10,11 +10,9 @@ classes = (
 )
 
 
-
 def register():
     bpy.types.Scene.COBieProperties = bpy.props.PointerProperty(type=prop.COBieProperties)
 
 
 def unregister():
     del bpy.types.Scene.COBieProperties
-
diff --git a/src/ifcblenderexport/blenderbim/bim/module/pset/__init__.py b/src/ifcblenderexport/blenderbim/bim/module/pset/__init__.py
index 31724d5e7b..d4a42735be 100644
--- a/src/ifcblenderexport/blenderbim/bim/module/pset/__init__.py
+++ b/src/ifcblenderexport/blenderbim/bim/module/pset/__init__.py
@@ -1,5 +1,5 @@
 import bpy
-from . import ui, operator
+from . import ui, prop, operator
 
 classes = (
     operator.TogglePsetExpansion,
@@ -8,13 +8,17 @@ classes = (
     operator.EditPset,
     operator.RemovePset,
     operator.AddPset,
+    operator.AddQto,
+    operator.GuessQuantity,
+    prop.PsetProperties,
     ui.BIM_PT_object_psets,
+    ui.BIM_PT_object_qtos,
 )
 
 
 def register():
-    pass
+    bpy.types.Object.PsetProperties = bpy.props.PointerProperty(type=prop.PsetProperties)
 
 
 def unregister():
-    pass
+    del bpy.types.Object.PsetProperties
diff --git a/src/ifcblenderexport/blenderbim/bim/module/pset/add_qto.py b/src/ifcblenderexport/blenderbim/bim/module/pset/add_qto.py
new file mode 100644
index 0000000000..5df089d98e
--- /dev/null
+++ b/src/ifcblenderexport/blenderbim/bim/module/pset/add_qto.py
@@ -0,0 +1,25 @@
+import ifcopenshell
+import blenderbim.bim.schema  # TODO: refactor
+
+
+class Usecase:
+    def __init__(self, file, settings=None):
+        self.file = file
+        self.settings = {"product": None, "Name": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        if self.settings["product"].is_a("IfcObject"):
+            qto = self.file.create_entity(
+                "IfcElementQuantity", **{"GlobalId": ifcopenshell.guid.new(), "Name": self.settings["Name"]}
+            )
+            self.file.create_entity(
+                "IfcRelDefinesByProperties",
+                **{
+                    "GlobalId": ifcopenshell.guid.new(),
+                    # TODO: owner history
+                    "RelatedObjects": [self.settings["product"]],
+                    "RelatingPropertyDefinition": qto,
+                }
+            )
diff --git a/src/ifcblenderexport/blenderbim/bim/module/pset/data.py b/src/ifcblenderexport/blenderbim/bim/module/pset/data.py
index d936db0e50..5c350f56f6 100644
--- a/src/ifcblenderexport/blenderbim/bim/module/pset/data.py
+++ b/src/ifcblenderexport/blenderbim/bim/module/pset/data.py
@@ -6,6 +6,7 @@ from blenderbim.bim.ifc import IfcStore
 class Data:
     products = {}
     psets = {}
+    qtos = {}
 
     @classmethod
     def load(cls, product_id):
@@ -13,7 +14,7 @@ class Data:
         if not file:
             return
         product = file.by_id(product_id)
-        cls.products[product_id] = set()
+        cls.products[product_id] = {"psets": set(), "qtos": set()}
         if product.is_a("IfcElementType"):
             cls.add_type_product_psets(product, product_id)
         else:
@@ -36,47 +37,18 @@ class Data:
                 continue
             if definition.RelatingPropertyDefinition.is_a("IfcPropertySet"):
                 cls.add_pset(definition.RelatingPropertyDefinition, product_id)
+            elif definition.RelatingPropertyDefinition.is_a("IfcElementQuantity"):
+                cls.add_qto(definition.RelatingPropertyDefinition, product_id)
 
     @classmethod
     def add_pset(cls, pset, product_id):
         new_pset = {
             "Name": pset.Name,
             "is_expanded": True,
-            "Properties": []
+            "Properties": cls.get_properties_from_template(pset.Name) or []
         }
-        cls.products[product_id].add(int(pset.id()))
+        cls.products[product_id]["psets"].add(int(pset.id()))
         cls.psets[int(pset.id())] = new_pset
-        pset_template = blenderbim.bim.schema.ifc.psetqto.get_by_name(pset.Name)
-        if pset_template:
-            for prop_template in pset_template.HasPropertyTemplates:
-                if not prop_template.is_a("IfcSimplePropertyTemplate"):
-                    continue # Other types not yet supported
-                enum_items = []
-                if prop_template.TemplateType == "P_SINGLEVALUE":
-                    data_type = str(IfcStore.get_schema().declaration_by_name(prop_template.PrimaryMeasureType))
-                elif prop_template.TemplateType == "P_ENUMERATEDVALUE":
-                    data_type = "enum"
-                    enum_items = [v.wrappedValue for v in prop_template.Enumerators.EnumerationValues]
-                else:
-                    continue # Other types not yet supported
-                if "<string>" in data_type:
-                    data_type = "string"
-                elif "<real>" in data_type:
-                    data_type = "float"
-                elif "<integer>" in data_type:
-                    data_type = "integer"
-                elif "<boolean>" in data_type:
-                    data_type = "boolean"
-                elif "<enumeration" in data_type:
-                    data_type = "enum"
-                    enum_items = attribute.type_of_attribute().declared_type().enumeration_items()
-                new_pset["Properties"].append({
-                    "Name": prop_template.Name,
-                    "value": None,
-                    "type": data_type,
-                    "enum_items": enum_items,
-                    "is_null": True
-                })
         try:
             if hasattr(pset, "HasProperties"):
                 props = pset.HasProperties
@@ -127,3 +99,74 @@ class Data:
                         "enum_items": [],
                         "is_null": prop.NominalValue.wrappedValue is None
                     })
+
+    @classmethod
+    def add_qto(cls, qto, product_id):
+        new_qto = {
+            "Name": qto.Name,
+            "is_expanded": True,
+            "Properties": cls.get_properties_from_template(qto.Name) or []
+        }
+        cls.products[product_id]["qtos"].add(int(qto.id()))
+        cls.qtos[int(qto.id())] = new_qto
+        for prop in qto.Quantities or []:
+            if prop.is_a("IfcPhysicalSimpleQuantity"):
+                value = prop[3]
+                has_existing_prop = False
+                for existing_prop in new_qto["Properties"]:
+                    if existing_prop["Name"] == prop.Name:
+                        existing_prop["value"] = float(value)
+                        existing_prop["is_null"] = value is None
+                        has_existing_prop = True
+                        break
+                if not has_existing_prop:
+                    new_qto["Properties"].append({
+                        "Name": prop.Name,
+                        "value": float(value),
+                        "type": "float",
+                        "enum_items": [],
+                        "is_null": value is None
+                    })
+
+    @classmethod
+    def get_properties_from_template(cls, name):
+        template = blenderbim.bim.schema.ifc.psetqto.get_by_name(name)
+        if not template:
+            return
+        properties = []
+        for prop_template in template.HasPropertyTemplates:
+            if not prop_template.is_a("IfcSimplePropertyTemplate"):
+                continue # Other types not yet supported
+            enum_items = []
+
+            if prop_template.TemplateType == "P_SINGLEVALUE":
+                data_type = str(IfcStore.get_schema().declaration_by_name(prop_template.PrimaryMeasureType or "IfcLabel"))
+            elif prop_template.TemplateType == "P_ENUMERATEDVALUE":
+                data_type = "enum"
+                enum_items = [v.wrappedValue for v in prop_template.Enumerators.EnumerationValues]
+            elif prop_template.TemplateType in ["Q_LENGTH", "Q_AREA", "Q_VOLUME", "Q_WEIGHT", "Q_TIME"]:
+                data_type = "float"
+            elif prop_template.TemplateType == "Q_COUNT":
+                data_type = "integer"
+            else:
+                continue # Other types not yet supported
+
+            if "<string>" in data_type:
+                data_type = "string"
+            elif "<real>" in data_type:
+                data_type = "float"
+            elif "<integer>" in data_type:
+                data_type = "integer"
+            elif "<boolean>" in data_type:
+                data_type = "boolean"
+            elif "<enumeration" in data_type:
+                data_type = "enum"
+                enum_items = attribute.type_of_attribute().declared_type().enumeration_items()
+            properties.append({
+                "Name": prop_template.Name,
+                "value": None,
+                "type": data_type,
+                "enum_items": enum_items,
+                "is_null": True
+            })
+        return properties
diff --git a/src/ifcblenderexport/blenderbim/bim/module/pset/edit_pset.py b/src/ifcblenderexport/blenderbim/bim/module/pset/edit_pset.py
index ccdef2ac48..0fc34751b1 100644
--- a/src/ifcblenderexport/blenderbim/bim/module/pset/edit_pset.py
+++ b/src/ifcblenderexport/blenderbim/bim/module/pset/edit_pset.py
@@ -9,47 +9,67 @@ class Usecase:
             self.settings[key] = value
 
     def execute(self):
-        if hasattr(self.settings["pset"], "HasProperties"):
-            attr_name = "HasProperties"
-        elif hasattr(self.settings["pset"], "Properties"):  # For IfcMaterialProperties
-            attr_name = "Properties"
-        props = getattr(self.settings["pset"], attr_name) or []
+        self.update_pset_name()
+        self.load_pset_template()
+        self.update_existing_properties()
+        new_properties = self.add_new_properties()
+        self.extend_pset_with_new_properties(new_properties)
 
+    def update_pset_name(self):
         if self.settings["Name"]:
             self.settings["pset"].Name = self.settings["Name"]
 
-        pset_template = blenderbim.bim.schema.ifc.psetqto.get_by_name(self.settings["pset"].Name)
+    def load_pset_template(self):
+        self.pset_template = blenderbim.bim.schema.ifc.psetqto.get_by_name(self.settings["pset"].Name)
 
-        for prop in props:
-            if prop.Name in self.settings["Properties"]:
-                value = self.settings["Properties"][prop.Name]
-                primary_measure_type = self.get_primary_measure_type(
-                    pset_template, prop.Name, previous_value=prop.NominalValue
-                )
-                if value is not None:
-                    prop.NominalValue = self.file.create_entity(primary_measure_type, value)
-                else:
-                    prop.NominalValue = None
-                del self.settings["Properties"][prop.Name]
+    def update_existing_properties(self):
+        for prop in self.get_properties():
+            self.update_existing_property(prop)
+
+    def update_existing_property(self, prop):
+        if prop.Name not in self.settings["Properties"]:
+            return
+        value = self.settings["Properties"][prop.Name]
+        if value is None:
+            prop.NominalValue = None
+        else:
+            primary_measure_type = self.get_primary_measure_type(prop.Name, previous_value=prop.NominalValue)
+            prop.NominalValue = self.file.create_entity(primary_measure_type, value)
+        del self.settings["Properties"][prop.Name]
+
+    def add_new_properties(self):
         properties = []
         for name, value in self.settings["Properties"].items():
             if value is None:
                 continue
-            primary_measure_type = self.get_primary_measure_type(pset_template, name)
+            primary_measure_type = self.get_primary_measure_type(name)
             properties.append(
                 self.file.create_entity(
                     "IfcPropertySingleValue",
                     **{"Name": name, "NominalValue": self.file.create_entity(primary_measure_type, value)},
                 )
             )
-        props = list(props)
-        props.extend(properties)
-        setattr(self.settings["pset"], attr_name, props)
+        return properties
 
-    def get_primary_measure_type(self, pset_template, name, previous_value=None):
-        if not pset_template:
+    def extend_pset_with_new_properties(self, new_properties):
+        props = list(self.get_properties())
+        props.extend(new_properties)
+        if hasattr(self.settings["pset"], "HasProperties"):
+            self.settings["pset"].HasProperties = props
+        elif hasattr(self.settings["pset"], "Properties"):
+            self.settings["pset"].Properties = props
+
+    def get_properties(self):
+        if hasattr(self.settings["pset"], "HasProperties"):
+            return self.settings["pset"].HasProperties or []
+        elif hasattr(self.settings["pset"], "Properties"):  # For IfcMaterialProperties
+            return self.settings["pset"].Properties or []
+
+    def get_primary_measure_type(self, name, previous_value=None):
+        if not self.pset_template:
             return previous_value.is_a() if previous_value else "IfcLabel"
-        for prop_template in pset_template.HasPropertyTemplates:
-            if prop_template.Name == name:
-                return prop_template.PrimaryMeasureType
+        for prop_template in self.pset_template.HasPropertyTemplates:
+            if prop_template.Name != name:
+                continue
+            return prop_template.PrimaryMeasureType or "IfcLabel"
         return previous_value.is_a() if previous_value else "IfcLabel"
diff --git a/src/ifcblenderexport/blenderbim/bim/module/pset/edit_qto.py b/src/ifcblenderexport/blenderbim/bim/module/pset/edit_qto.py
new file mode 100644
index 0000000000..95a672b850
--- /dev/null
+++ b/src/ifcblenderexport/blenderbim/bim/module/pset/edit_qto.py
@@ -0,0 +1,72 @@
+import blenderbim.bim.schema  # TODO: refactor
+
+
+class Usecase:
+    def __init__(self, file, settings=None):
+        self.file = file
+        self.settings = {"qto": None, "Name": None, "Properties": {}}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        self.update_qto_name()
+        self.load_qto_template()
+        self.update_existing_properties()
+        new_properties = self.add_new_properties()
+        self.extend_qto_with_new_properties(new_properties)
+
+    def update_qto_name(self):
+        if self.settings["Name"]:
+            self.settings["qto"].Name = self.settings["Name"]
+
+    def load_qto_template(self):
+        self.qto_template = blenderbim.bim.schema.ifc.psetqto.get_by_name(self.settings["qto"].Name)
+
+    def update_existing_properties(self):
+        for prop in self.settings["qto"].Quantities or []:
+            self.update_existing_property(prop)
+
+    def update_existing_property(self, prop):
+        if prop.Name not in self.settings["Properties"]:
+            return
+        value = self.settings["Properties"][prop.Name]
+        if prop.is_a("IfcPhysicalSimpleQuantity"):
+            prop[3] = float(value) if value else None
+        del self.settings["Properties"][prop.Name]
+
+    def add_new_properties(self):
+        properties = []
+        for name, value in self.settings["Properties"].items():
+            if value is None:
+                continue
+            property_type = self.get_canonical_property_type(name)
+            properties.append(
+                self.file.create_entity(
+                    "IfcQuantity{}".format(property_type),
+                    **{"Name": name, "{}Value".format(property_type): value},
+                )
+            )
+        return properties
+
+    def extend_qto_with_new_properties(self, new_properties):
+        props = list(self.settings["qto"].Quantities) if self.settings["qto"].Quantities else []
+        props.extend(new_properties)
+        self.settings["qto"].Quantities = props
+
+    def get_canonical_property_type(self, name):
+        if not self.qto_template:
+            return "Length"
+        for prop_template in self.qto_template.HasPropertyTemplates:
+            if prop_template.Name != name:
+                continue
+            return prop_template.TemplateType[2:].lower().capitalize()
+        return "Length"
+
+    def get_primary_measure_type(self, name, previous_value=None):
+        if not self.qto_template:
+            return previous_value.is_a() if previous_value else "IfcLabel"
+        for prop_template in self.qto_template.HasPropertyTemplates:
+            if prop_template.Name != name:
+                continue
+            return prop_template.PrimaryMeasureType or "IfcLabel"
+        return previous_value.is_a() if previous_value else "IfcLabel"
diff --git a/src/ifcblenderexport/blenderbim/bim/module/pset/operator.py b/src/ifcblenderexport/blenderbim/bim/module/pset/operator.py
index a0b02bf483..d1389c2004 100644
--- a/src/ifcblenderexport/blenderbim/bim/module/pset/operator.py
+++ b/src/ifcblenderexport/blenderbim/bim/module/pset/operator.py
@@ -1,10 +1,14 @@
 import bpy
 import json
+import ifcopenshell.util.unit
 import blenderbim.bim.module.pset.add_pset as add_pset
 import blenderbim.bim.module.pset.edit_pset as edit_pset
 import blenderbim.bim.module.pset.remove_pset as remove_pset
+import blenderbim.bim.module.pset.add_qto as add_qto
+import blenderbim.bim.module.pset.edit_qto as edit_qto
 from blenderbim.bim.ifc import IfcStore
 from blenderbim.bim.module.pset.data import Data
+from blenderbim.bim.module.pset.qto_calculator import QtoCalculator
 
 
 class TogglePsetExpansion(bpy.types.Operator):
@@ -14,8 +18,8 @@ class TogglePsetExpansion(bpy.types.Operator):
 
     def execute(self, context):
         obj = bpy.context.active_object
-        props = obj.BIMObjectProperties
-        Data.psets[self.pset_id]["is_expanded"] = not Data.psets[self.pset_id]["is_expanded"]
+        data = Data.psets if self.pset_id in Data.psets else Data.qtos
+        data[self.pset_id]["is_expanded"] = not data[self.pset_id]["is_expanded"]
         return {"FINISHED"}
 
 
@@ -26,13 +30,14 @@ class EnablePsetEditing(bpy.types.Operator):
 
     def execute(self, context):
         obj = bpy.context.active_object
-        props = obj.BIMObjectProperties
+        props = obj.PsetProperties
 
         while len(props.properties) > 0:
             props.properties.remove(0)
 
-        props.active_pset_name = Data.psets[self.pset_id]["Name"]
-        for prop in Data.psets[self.pset_id]["Properties"]:
+        data = Data.psets if self.pset_id in Data.psets else Data.qtos
+        props.active_pset_name = data[self.pset_id]["Name"]
+        for prop in data[self.pset_id]["Properties"]:
             new = props.properties.add()
             new.name = prop["Name"]
             new.is_null = prop["is_null"]
@@ -59,7 +64,7 @@ class DisablePsetEditing(bpy.types.Operator):
 
     def execute(self, context):
         obj = bpy.context.active_object
-        props = obj.BIMObjectProperties
+        props = obj.PsetProperties
         props.active_pset_id = 0
         return {"FINISHED"}
 
@@ -71,9 +76,11 @@ class EditPset(bpy.types.Operator):
     def execute(self, context):
         self.file = IfcStore.get_file()
         obj = bpy.context.active_object
-        props = obj.BIMObjectProperties
+        oprops = obj.BIMObjectProperties
+        props = obj.PsetProperties
         properties = {}
-        for prop in Data.psets[props.active_pset_id]["Properties"]:
+        data = Data.psets if props.active_pset_id in Data.psets else Data.qtos
+        for prop in data[props.active_pset_id]["Properties"]:
             blender_prop = props.properties.get(prop["Name"])
             if not blender_prop:
                 continue
@@ -89,12 +96,19 @@ class EditPset(bpy.types.Operator):
                 properties[prop["Name"]] = blender_prop.float_value
             elif prop["type"] == "enum":
                 properties[prop["Name"]] = blender_prop.enum_value
-        edit_pset.Usecase(self.file, {
-            "pset": self.file.by_id(props.active_pset_id),
-            "Name": props.active_pset_name,
-            "Properties": properties
-        }).execute()
-        Data.load(props.ifc_definition_id)
+        if props.active_pset_id in Data.psets:
+            edit_pset.Usecase(self.file, {
+                "pset": self.file.by_id(props.active_pset_id),
+                "Name": props.active_pset_name,
+                "Properties": properties
+            }).execute()
+        else:
+            edit_qto.Usecase(self.file, {
+                "qto": self.file.by_id(props.active_pset_id),
+                "Name": props.active_pset_name,
+                "Properties": properties
+            }).execute()
+        Data.load(oprops.ifc_definition_id)
         bpy.ops.bim.disable_pset_editing()
         return {"FINISHED"}
 
@@ -123,10 +137,72 @@ class AddPset(bpy.types.Operator):
     def execute(self, context):
         self.file = IfcStore.get_file()
         obj = bpy.context.active_object
-        props = obj.BIMObjectProperties
+        oprops = obj.BIMObjectProperties
+        props = obj.PsetProperties
         add_pset.Usecase(self.file, {
-            "product": self.file.by_id(props.ifc_definition_id),
+            "product": self.file.by_id(oprops.ifc_definition_id),
             "Name": props.pset_name,
         }).execute()
-        Data.load(props.ifc_definition_id)
+        Data.load(oprops.ifc_definition_id)
         return {"FINISHED"}
+
+
+class AddQto(bpy.types.Operator):
+    bl_idname = "bim.add_qto"
+    bl_label = "Add Qto"
+
+    def execute(self, context):
+        self.file = IfcStore.get_file()
+        obj = bpy.context.active_object
+        oprops = obj.BIMObjectProperties
+        props = obj.PsetProperties
+        add_qto.Usecase(self.file, {
+            "product": self.file.by_id(oprops.ifc_definition_id),
+            "Name": props.qto_name,
+        }).execute()
+        Data.load(oprops.ifc_definition_id)
+        return {"FINISHED"}
+
+
+class GuessQuantity(bpy.types.Operator):
+    bl_idname = "bim.guess_quantity"
+    bl_label = "Guess Quantity"
+    prop: bpy.props.StringProperty()
+
+    def execute(self, context):
+        self.qto_calculator = QtoCalculator()
+        obj = bpy.context.active_object
+        prop = obj.PsetProperties.properties.get(self.prop)
+        prop.float_value = self.guess_quantity(obj)
+        return {"FINISHED"}
+
+    def guess_quantity(self, obj):
+        quantity = self.qto_calculator.guess_quantity(self.prop, [p.name for p in obj.PsetProperties.properties], obj)
+        if "area" in self.prop.lower():
+            if bpy.context.scene.BIMProperties.area_unit:
+                prefix, name = self.get_prefix_name(bpy.context.scene.BIMProperties.area_unit)
+                quantity = ifcopenshell.util.unit.convert(quantity, None, "SQUARE_METRE", prefix, name)
+        elif "volume" in self.prop.lower():
+            if bpy.context.scene.BIMProperties.volume_unit:
+                prefix, name = self.get_prefix_name(bpy.context.scene.BIMProperties.volume_unit)
+                quantity = ifcopenshell.util.unit.convert(quantity, None, "CUBIC_METRE", prefix, name)
+        else:
+            prefix, name = self.get_blender_prefix_name()
+            quantity = ifcopenshell.util.unit.convert(quantity, None, "METRE", prefix, name)
+        return round(quantity, 3)
+
+    def get_prefix_name(self, value):
+        if "/" in value:
+            return value.split("/")
+        return None, value
+
+    def get_blender_prefix_name(self):
+        if bpy.context.scene.unit_settings.system == "IMPERIAL":
+            if bpy.context.scene.unit_settings.length_unit == "INCHES":
+                return None, "inch"
+            elif bpy.context.scene.unit_settings.length_unit == "FEET":
+                return None, "foot"
+        elif bpy.context.scene.unit_settings.system == "METRIC":
+            if bpy.context.scene.unit_settings.length_unit == "METERS":
+                return None, "METRE"
+            return bpy.context.scene.unit_settings.length_unit[0 : -len("METERS")], "METRE"
diff --git a/src/ifcblenderexport/blenderbim/bim/module/pset/prop.py b/src/ifcblenderexport/blenderbim/bim/module/pset/prop.py
new file mode 100644
index 0000000000..8762af706c
--- /dev/null
+++ b/src/ifcblenderexport/blenderbim/bim/module/pset/prop.py
@@ -0,0 +1,48 @@
+import bpy
+from blenderbim.bim.prop import Attribute
+import blenderbim.bim.schema
+from bpy.types import PropertyGroup
+from bpy.props import (
+    PointerProperty,
+    StringProperty,
+    EnumProperty,
+    BoolProperty,
+    IntProperty,
+    FloatProperty,
+    FloatVectorProperty,
+    CollectionProperty,
+)
+
+
+psetnames = {}
+qtonames = {}
+
+
+def getPsetNames(self, context):
+    global psetnames
+    if "/" in context.active_object.name:
+        ifc_class = context.active_object.name.split("/")[0]
+        if ifc_class not in psetnames:
+            psets = blenderbim.bim.schema.ifc.psetqto.get_applicable(ifc_class, pset_only=True)
+            psetnames[ifc_class] = [(p.Name, p.Name, "") for p in psets]
+        return psetnames[ifc_class]
+    return []
+
+
+def getQtoNames(self, context):
+    global qtonames
+    if "/" in context.active_object.name:
+        ifc_class = context.active_object.name.split("/")[0]
+        if ifc_class not in qtonames:
+            psets = blenderbim.bim.schema.ifc.psetqto.get_applicable(ifc_class, qto_only=True)
+            qtonames[ifc_class] = [(p.Name, p.Name, "") for p in psets]
+        return qtonames[ifc_class]
+    return []
+
+
+class PsetProperties(PropertyGroup):
+    active_pset_id: IntProperty(name="Active Pset ID")
+    active_pset_name: StringProperty(name="Pset Name")
+    properties: CollectionProperty(name="Properties", type=Attribute)
+    pset_name: EnumProperty(items=getPsetNames, name="Pset Name")
+    qto_name: EnumProperty(items=getQtoNames, name="Qto Name")
diff --git a/src/ifcblenderexport/blenderbim/bim/qto.py b/src/ifcblenderexport/blenderbim/bim/module/pset/qto_calculator.py
similarity index 100%
rename from src/ifcblenderexport/blenderbim/bim/qto.py
rename to src/ifcblenderexport/blenderbim/bim/module/pset/qto_calculator.py
diff --git a/src/ifcblenderexport/blenderbim/bim/module/pset/ui.py b/src/ifcblenderexport/blenderbim/bim/module/pset/ui.py
index 43411fa14b..37b8567583 100644
--- a/src/ifcblenderexport/blenderbim/bim/module/pset/ui.py
+++ b/src/ifcblenderexport/blenderbim/bim/module/pset/ui.py
@@ -1,6 +1,64 @@
 from bpy.types import Panel
 from blenderbim.bim.module.pset.data import Data
 
+def draw_psetqto_ui(pset_id, pset, props, layout):
+    box = layout.box()
+    row = box.row(align=True)
+    icon = "TRIA_DOWN" if pset["is_expanded"] else "TRIA_RIGHT"
+    row.operator("bim.toggle_pset_expansion", icon=icon, text="", emboss=False).pset_id = pset_id
+    if not props.active_pset_id:
+        row.label(text=pset["Name"], icon="COPY_ID")
+        row.operator("bim.enable_pset_editing", icon="GREASEPENCIL", text="").pset_id = pset_id
+        row.operator("bim.remove_pset", icon="X", text="").pset_id = pset_id
+    elif props.active_pset_id != pset_id:
+        row.label(text=pset["Name"], icon="COPY_ID")
+        row.operator("bim.remove_pset", icon="X", text="").pset_id = pset_id
+    elif props.active_pset_id == pset_id:
+        row.prop(props, "active_pset_name", icon="COPY_ID", text="")
+        row.operator("bim.edit_pset", icon="CHECKMARK", text="")
+        row.operator("bim.disable_pset_editing", icon="X", text="")
+    if pset["is_expanded"]:
+        if props.active_pset_id == pset_id:
+            for prop in pset["Properties"]:
+                draw_psetqto_editable_ui(box, props, prop)
+        else:
+            for prop in pset["Properties"]:
+                if prop["value"] is None or prop["value"] == "":
+                    continue
+                row = box.row(align=True)
+                row.scale_y = 0.8
+                row.label(text=prop["Name"])
+                row.label(text=str(prop["value"]))
+
+def draw_psetqto_editable_ui(box, props, prop):
+    row = box.row(align=True)
+    blender_prop = props.properties.get(prop["Name"])
+    if prop["type"] == "string":
+        row.prop(blender_prop, "string_value", text=prop["Name"])
+    elif prop["type"] == "integer":
+        row.prop(blender_prop, "int_value", text=prop["Name"])
+    elif prop["type"] == "float":
+        row.prop(blender_prop, "float_value", text=prop["Name"])
+    elif prop["type"] == "boolean":
+        row.prop(blender_prop, "bool_value", text=prop["Name"])
+    elif prop["type"] == "enum":
+        row.prop(blender_prop, "enum_value", text=prop["Name"])
+    row.prop(blender_prop, "is_null", icon="RADIOBUT_OFF" if blender_prop.is_null else "RADIOBUT_ON", text="")
+    if (
+        "length" in prop["Name"].lower()
+        or "width" in prop["Name"].lower()
+        or "height" in prop["Name"].lower()
+        or "depth" in prop["Name"].lower()
+        or "perimeter" in prop["Name"].lower()
+    ):
+        op = row.operator("bim.guess_quantity", icon="IPO_EASE_IN_OUT", text="")
+        op.prop = prop["Name"]
+    elif "area" in prop["Name"].lower():
+        op = row.operator("bim.guess_quantity", icon="MESH_CIRCLE", text="")
+        op.prop = prop["Name"]
+    elif "volume" in prop["Name"].lower():
+        op = row.operator("bim.guess_quantity", icon="SPHERE", text="")
+        op.prop = prop["Name"]
 
 class BIM_PT_object_psets(Panel):
     bl_label = "IFC Object Property Sets"
@@ -23,61 +81,57 @@ class BIM_PT_object_psets(Panel):
         return True
 
     def draw(self, context):
-        props = context.active_object.BIMObjectProperties
-        if not props.ifc_definition_id:
+        oprops = context.active_object.BIMObjectProperties
+        props = context.active_object.PsetProperties
+        if not oprops.ifc_definition_id:
             return
-        if props.ifc_definition_id not in Data.products:
-            Data.load(props.ifc_definition_id)
+        if oprops.ifc_definition_id not in Data.products:
+            Data.load(oprops.ifc_definition_id)
         row = self.layout.row(align=True)
         row.prop(props, "pset_name", text="")
         row.operator("bim.add_pset", icon="ADD", text="")
 
-        self.draw_psets_ui(props, Data.products[props.ifc_definition_id])
+        for pset_id in Data.products[oprops.ifc_definition_id]["psets"]:
+            pset = Data.psets[pset_id]
+            draw_psetqto_ui(pset_id, pset, props, self.layout)
 
         # TODO reimplement. See #1222.
-        #if props.relating_type and props.relating_type.BIMObjectProperties.psets:
+        #if props.relating_type and props.relating_type.PsetProperties.psets:
         #    self.layout.label(text="Inherited Psets:")
-        #    self.draw_psets_ui(props.relating_type.BIMObjectProperties, enabled=False)
+        #    self.draw_psets_ui(props.relating_type.PsetProperties, enabled=False)
 
-    def draw_psets_ui(self, props, pset_ids):
-        for pset_id in pset_ids:
-            pset = Data.psets[pset_id]
-            box = self.layout.box()
-            row = box.row(align=True)
-            icon = "TRIA_DOWN" if pset["is_expanded"] else "TRIA_RIGHT"
-            row.operator("bim.toggle_pset_expansion", icon=icon, text="", emboss=False).pset_id = pset_id
-            if not props.active_pset_id:
-                row.label(text=pset["Name"], icon="COPY_ID")
-                row.operator("bim.enable_pset_editing", icon="GREASEPENCIL", text="").pset_id = pset_id
-                row.operator("bim.remove_pset", icon="X", text="").pset_id = pset_id
-            elif props.active_pset_id != pset_id:
-                row.label(text=pset["Name"], icon="COPY_ID")
-                row.operator("bim.remove_pset", icon="X", text="").pset_id = pset_id
-            elif props.active_pset_id == pset_id:
-                row.prop(props, "active_pset_name", icon="COPY_ID", text="")
-                row.operator("bim.edit_pset", icon="CHECKMARK", text="")
-                row.operator("bim.disable_pset_editing", icon="X", text="")
-            if pset["is_expanded"]:
-                if props.active_pset_id == pset_id:
-                    for prop in pset["Properties"]:
-                        row = box.row(align=True)
-                        blender_prop = props.properties.get(prop["Name"])
-                        if prop["type"] == "string":
-                            row.prop(blender_prop, "string_value", text=prop["Name"])
-                        elif prop["type"] == "integer":
-                            row.prop(blender_prop, "int_value", text=prop["Name"])
-                        elif prop["type"] == "float":
-                            row.prop(blender_prop, "float_value", text=prop["Name"])
-                        elif prop["type"] == "boolean":
-                            row.prop(blender_prop, "bool_value", text=prop["Name"])
-                        elif prop["type"] == "enum":
-                            row.prop(blender_prop, "enum_value", text=prop["Name"])
-                        row.prop(blender_prop, "is_null", icon="RADIOBUT_OFF" if blender_prop.is_null else "RADIOBUT_ON", text="")
-                else:
-                    for prop in pset["Properties"]:
-                        if prop["value"] is None or prop["value"] == "":
-                            continue
-                        row = box.row(align=True)
-                        row.scale_y = 0.8
-                        row.label(text=prop["Name"])
-                        row.label(text=str(prop["value"]))
+
+class BIM_PT_object_qtos(Panel):
+    bl_label = "IFC Object Quantity Sets"
+    bl_idname = "BIM_PT_object_qtos"
+    bl_space_type = "PROPERTIES"
+    bl_region_type = "WINDOW"
+    bl_context = "object"
+
+    @classmethod
+    def poll(cls, context):
+        if not context.active_object:
+            return False
+        props = context.active_object.BIMObjectProperties
+        if not props.ifc_definition_id:
+            return False
+        if props.ifc_definition_id not in Data.products:
+            Data.load(props.ifc_definition_id)
+        if not Data.products[props.ifc_definition_id]:
+            return False
+        return True
+
+    def draw(self, context):
+        oprops = context.active_object.BIMObjectProperties
+        props = context.active_object.PsetProperties
+        if not oprops.ifc_definition_id:
+            return
+        if oprops.ifc_definition_id not in Data.products:
+            Data.load(oprops.ifc_definition_id)
+        row = self.layout.row(align=True)
+        row.prop(props, "qto_name", text="")
+        row.operator("bim.add_qto", icon="ADD", text="")
+
+        for qto_id in Data.products[oprops.ifc_definition_id]["qtos"]:
+            qto = Data.qtos[qto_id]
+            draw_psetqto_ui(qto_id, qto, props, self.layout)
diff --git a/src/ifcblenderexport/blenderbim/bim/operator.py b/src/ifcblenderexport/blenderbim/bim/operator.py
index e684639e3f..a5c284529d 100644
--- a/src/ifcblenderexport/blenderbim/bim/operator.py
+++ b/src/ifcblenderexport/blenderbim/bim/operator.py
@@ -105,7 +105,7 @@ class ExportIFC(bpy.types.Operator):
         else:
             output_file = bpy.path.ensure_ext(self.filepath, ".ifc")
         ifc_export_settings = export_ifc.IfcExportSettings.factory(context, output_file, logger)
-        qto_calculator = qto.QtoCalculator()
+        qto_calculator = None # TODO: remove from export
         ifc_parser = export_ifc.IfcParser(ifc_export_settings, qto_calculator)
         ifc_exporter = export_ifc.IfcExporter(ifc_export_settings, ifc_parser)
         ifc_export_settings.logger.info("Starting export")
@@ -2805,70 +2805,6 @@ class ConvertGlobalToLocal(bpy.types.Operator):
         return {"FINISHED"}
 
 
-class GuessQuantity(bpy.types.Operator):
-    bl_idname = "bim.guess_quantity"
-    bl_label = "Guess Quantity"
-    qto_index: bpy.props.IntProperty()
-    prop_index: bpy.props.IntProperty()
-
-    def execute(self, context):
-        self.qto_calculator = qto.QtoCalculator()
-        source_qto = bpy.context.active_object.BIMObjectProperties.qtos[self.qto_index]
-        props = source_qto.properties
-        prop = props[self.prop_index]
-        for obj in bpy.context.selected_objects:
-            dest_qto = obj.BIMObjectProperties.qtos.get(source_qto.name)
-            if not dest_qto:
-                if source_qto.name not in obj.BIMObjectProperties.qto_name:
-                    continue
-                dest_qto = self.add_qto(obj, source_qto.name)
-            prop = dest_qto.properties.get(prop.name)
-            self.guess_quantity(obj, prop, props)
-        return {"FINISHED"}
-
-    def guess_quantity(self, obj, prop, props):
-        quantity = self.qto_calculator.guess_quantity(prop.name, [p.name for p in props], obj)
-        if "area" in prop.name.lower():
-            if bpy.context.scene.BIMProperties.area_unit:
-                prefix, name = self.get_prefix_name(bpy.context.scene.BIMProperties.area_unit)
-                quantity = helper.SIUnitHelper.convert(quantity, None, "SQUARE_METRE", prefix, name)
-        elif "volume" in prop.name.lower():
-            if bpy.context.scene.BIMProperties.volume_unit:
-                prefix, name = self.get_prefix_name(bpy.context.scene.BIMProperties.volume_unit)
-                quantity = helper.SIUnitHelper.convert(quantity, None, "CUBIC_METRE", prefix, name)
-        else:
-            prefix, name = self.get_blender_prefix_name()
-            quantity = helper.SIUnitHelper.convert(quantity, None, "METRE", prefix, name)
-        prop.string_value = str(round(quantity, 3))
-
-    def add_qto(self, obj, name):
-        qto_template = schema.ifc.psetqto.get_by_name(name)
-        if not qto_template:
-            return
-        qto = obj.BIMObjectProperties.qtos.add()
-        qto.name = name
-        for prop_name in (p.Name for p in qto_template.HasPropertyTemplates):
-            prop = qto.properties.add()
-            prop.name = prop_name
-        return qto
-
-    def get_prefix_name(self, value):
-        if "/" in value:
-            return value.split("/")
-        return None, value
-
-    def get_blender_prefix_name(self):
-        if bpy.context.scene.unit_settings.system == "IMPERIAL":
-            if bpy.context.scene.unit_settings.length_unit == "INCHES":
-                return None, "inch"
-            elif bpy.context.scene.unit_settings.length_unit == "FEET":
-                return None, "foot"
-        elif bpy.context.scene.unit_settings.system == "METRIC":
-            if bpy.context.scene.unit_settings.length_unit == "METERS":
-                return None, "METRE"
-            return bpy.context.scene.unit_settings.length_unit[0 : -len("METERS")], "METRE"
-
-
 class ExecuteBIMTester(bpy.types.Operator):
     bl_idname = "bim.execute_bim_tester"
     bl_label = "Execute BIMTester"
@@ -2982,6 +2918,7 @@ class CalculateObjectVolumes(bpy.types.Operator):
     bl_label = "Calculate Object Volumes"
 
     def execute(self, context):
+        # TODO: reimplement
         qto_calculator = qto.QtoCalculator()
         result = 0
         for obj in bpy.context.selected_objects:
diff --git a/src/ifcblenderexport/blenderbim/bim/prop.py b/src/ifcblenderexport/blenderbim/bim/prop.py
index 5b7540b865..7f06227817 100644
--- a/src/ifcblenderexport/blenderbim/bim/prop.py
+++ b/src/ifcblenderexport/blenderbim/bim/prop.py
@@ -40,8 +40,6 @@ psettemplatefiles_enum = []
 propertysettemplates_enum = []
 classification_enum = []
 attributes_enum = []
-psetnames = {}
-qtonames_enum = []
 materialattributes_enum = []
 materialtypes_enum = []
 contexts_enum = []
@@ -445,17 +443,6 @@ def refreshReferences(self, context):
     context.scene.BIMProperties.classification_references.root = ""
 
 
-def getPsetNames(self, context):
-    global psetnames
-    if "/" in context.active_object.name:
-        ifc_class = context.active_object.name.split("/")[0]
-        if ifc_class not in psetnames:
-            psets = schema.ifc.psetqto.get_applicable(ifc_class, pset_only=True)
-            psetnames[ifc_class] = [(p.Name, p.Name, "") for p in psets]
-        return psetnames[ifc_class]
-    return []
-
-
 def getMaterialPsetNames(self, context):
     global materialpsetnames_enum
     materialpsetnames_enum.clear()
@@ -464,15 +451,6 @@ def getMaterialPsetNames(self, context):
     return materialpsetnames_enum
 
 
-def getQtoNames(self, context):
-    global qtonames_enum
-    qtonames_enum.clear()
-    if "/" in context.active_object.name and context.active_object.name.split("/")[0] in schema.ifc.elements:
-        qto_names = schema.ifc.psetqto.get_applicable_names(context.active_object.name.split("/")[0], qto_only=True)
-        qtonames_enum.extend([(q, q, "") for q in qto_names])
-    return qtonames_enum
-
-
 def getApplicableMaterialAttributes(self, context):
     global materialattributes_enum
     materialattributes_enum.clear()
@@ -1492,9 +1470,6 @@ class BIMObjectProperties(PropertyGroup):
     is_editing_type: BoolProperty(name="Is Editing Type")
     relating_type: PointerProperty(name="Type Product", type=bpy.types.Object)
     relating_structure: PointerProperty(name="Spatial Container", type=bpy.types.Object)
-    active_pset_id: IntProperty(name="Active Pset ID")
-    active_pset_name: StringProperty(name="Pset Name")
-    properties: CollectionProperty(name="Properties", type=Attribute)
     psets: CollectionProperty(name="Psets", type=PsetQto)
     qtos: CollectionProperty(name="Qtos", type=PsetQto)
     document_references: CollectionProperty(name="Document References", type=DocumentReference)
@@ -1505,8 +1480,6 @@ class BIMObjectProperties(PropertyGroup):
     material_type: EnumProperty(items=getMaterialTypes, name="Material Type")
     material: PointerProperty(name="Material", type=bpy.types.Material)
     material_set: PointerProperty(name="Material Set", type=MaterialSet)
-    pset_name: EnumProperty(items=getPsetNames, name="Pset Name")
-    qto_name: EnumProperty(items=getQtoNames, name="Qto Name")
     has_boundary_condition: BoolProperty(name="Has Boundary Condition")
     boundary_condition: PointerProperty(name="Boundary Condition", type=BoundaryCondition)
     structural_member_connection: PointerProperty(name="Structural Member Connection", type=bpy.types.Object)
diff --git a/src/ifcblenderexport/blenderbim/bim/ui.py b/src/ifcblenderexport/blenderbim/bim/ui.py
index d4e843a38e..0adcd72b36 100644
--- a/src/ifcblenderexport/blenderbim/bim/ui.py
+++ b/src/ifcblenderexport/blenderbim/bim/ui.py
@@ -143,61 +143,6 @@ class BIM_PT_object_material(Panel):
                     row.prop(attribute, "string_value", text="")
 
 
-class BIM_PT_object_qto(Panel):
-    bl_label = "IFC Object Quantity Sets"
-    bl_idname = "BIM_PT_object_qto"
-    bl_space_type = "PROPERTIES"
-    bl_region_type = "WINDOW"
-    bl_context = "object"
-
-    @classmethod
-    def poll(cls, context):
-        return context.active_object is not None and hasattr(context.active_object, "BIMObjectProperties")
-
-    def draw(self, context):
-        if context.active_object is None:
-            return
-        layout = self.layout
-        props = context.active_object.BIMObjectProperties
-        row = layout.row(align=True)
-        row.prop(props, "qto_name", text="")
-        row.operator("bim.add_qto")
-
-        for index, qto in enumerate(props.qtos):
-            box = self.layout.box()
-            row = box.row(align=True)
-
-            row.prop(
-                qto, "is_expanded", icon="TRIA_DOWN" if qto.is_expanded else "TRIA_RIGHT", icon_only=True, emboss=False
-            )
-            row.prop(qto, "name", text="", icon="COPY_ID")
-            row.operator("bim.remove_qto", icon="X", text="").index = index
-            if not qto.is_expanded:
-                continue
-            for index2, prop in enumerate(qto.properties):
-                row = box.row(align=True)
-                row.prop(prop, "name", text="")
-                row.prop(prop, "string_value", text="")
-                if (
-                    "length" in prop.name.lower()
-                    or "width" in prop.name.lower()
-                    or "height" in prop.name.lower()
-                    or "depth" in prop.name.lower()
-                    or "perimeter" in prop.name.lower()
-                ):
-                    op = row.operator("bim.guess_quantity", icon="IPO_EASE_IN_OUT", text="")
-                    op.qto_index = index
-                    op.prop_index = index2
-                elif "area" in prop.name.lower():
-                    op = row.operator("bim.guess_quantity", icon="MESH_CIRCLE", text="")
-                    op.qto_index = index
-                    op.prop_index = index2
-                elif "volume" in prop.name.lower():
-                    op = row.operator("bim.guess_quantity", icon="SPHERE", text="")
-                    op.qto_index = index
-                    op.prop_index = index2
-
-
 class BIM_PT_object_structural(Panel):
     bl_label = "IFC Structural Relationships"
     bl_idname = "BIM_PT_object_structural"