diff --git a/src/main/java/net/fortuna/ical4j/extensions/property/Categories.java b/src/main/java/net/fortuna/ical4j/extensions/property/Categories.java
deleted file mode 100644
index 5319c32..0000000
--- a/src/main/java/net/fortuna/ical4j/extensions/property/Categories.java
+++ /dev/null
@@ -1,54 +0,0 @@
-package net.fortuna.ical4j.extensions.property;
-
-import net.fortuna.ical4j.model.*;
-
-/**
- * Created by fortuna on 11/09/15.
- */
-public class Categories extends Property {
-
-    private static final long serialVersionUID = 1L;
-
-    public static final String PROPERTY_NAME = "CATEGORIES";
-
-    private String value;
-
-    public Categories() {
-        super(PROPERTY_NAME, PropertyFactoryImpl.getInstance());
-    }
-
-    public Categories(ParameterList params, String value) {
-        super(PROPERTY_NAME, params, PropertyFactoryImpl.getInstance());
-        setValue(value);
-    }
-
-    @Override
-    public void setValue(String aValue) {
-        this.value = aValue;
-    }
-
-    @Override
-    public void validate() throws ValidationException {
-
-    }
-
-    @Override
-    public String getValue() {
-        return value;
-    }
-
-    public static class Factory extends Content.Factory implements PropertyFactory<Categories> {
-        public Factory() {
-            super(PROPERTY_NAME);
-        }
-
-        public Categories createProperty() {
-            return new Categories();
-        }
-
-        public Categories createProperty(ParameterList parameters, String value) {
-            Categories property = new Categories(parameters, value);
-            return property;
-        }
-    }
-}
diff --git a/src/main/java/net/fortuna/ical4j/extensions/property/Description.java b/src/main/java/net/fortuna/ical4j/extensions/property/Description.java
deleted file mode 100644
index b6cb441..0000000
--- a/src/main/java/net/fortuna/ical4j/extensions/property/Description.java
+++ /dev/null
@@ -1,54 +0,0 @@
-package net.fortuna.ical4j.extensions.property;
-
-import net.fortuna.ical4j.model.*;
-
-/**
- * Created by fortuna on 11/09/15.
- */
-public class Description extends Property {
-
-    private static final long serialVersionUID = 1L;
-
-    public static final String PROPERTY_NAME = "DESCRIPTION";
-
-    private String value;
-
-    public Description() {
-        super(PROPERTY_NAME, PropertyFactoryImpl.getInstance());
-    }
-
-    public Description(ParameterList params, String value) {
-        super(PROPERTY_NAME, params, PropertyFactoryImpl.getInstance());
-        setValue(value);
-    }
-
-    @Override
-    public void setValue(String aValue) {
-        this.value = aValue;
-    }
-
-    @Override
-    public void validate() throws ValidationException {
-
-    }
-
-    @Override
-    public String getValue() {
-        return value;
-    }
-
-    public static class Factory extends Content.Factory implements PropertyFactory<Description> {
-        public Factory() {
-            super(PROPERTY_NAME);
-        }
-
-        public Description createProperty() {
-            return new Description();
-        }
-
-        public Description createProperty(ParameterList parameters, String value) {
-            Description property = new Description(parameters, value);
-            return property;
-        }
-    }
-}
diff --git a/src/main/java/net/fortuna/ical4j/extensions/property/LastModified.java b/src/main/java/net/fortuna/ical4j/extensions/property/LastModified.java
deleted file mode 100644
index 644f615..0000000
--- a/src/main/java/net/fortuna/ical4j/extensions/property/LastModified.java
+++ /dev/null
@@ -1,54 +0,0 @@
-package net.fortuna.ical4j.extensions.property;
-
-import net.fortuna.ical4j.model.*;
-
-/**
- * Created by fortuna on 11/09/15.
- */
-public class LastModified extends Property {
-
-    private static final long serialVersionUID = 1L;
-
-    public static final String PROPERTY_NAME = "LAST-MODIFIED";
-
-    private String value;
-
-    public LastModified() {
-        super(PROPERTY_NAME, PropertyFactoryImpl.getInstance());
-    }
-
-    public LastModified(ParameterList params, String value) {
-        super(PROPERTY_NAME, params, PropertyFactoryImpl.getInstance());
-        setValue(value);
-    }
-
-    @Override
-    public void setValue(String aValue) {
-        this.value = aValue;
-    }
-
-    @Override
-    public void validate() throws ValidationException {
-
-    }
-
-    @Override
-    public String getValue() {
-        return value;
-    }
-
-    public static class Factory extends Content.Factory implements PropertyFactory<LastModified> {
-        public Factory() {
-            super(PROPERTY_NAME);
-        }
-
-        public LastModified createProperty() {
-            return new LastModified();
-        }
-
-        public LastModified createProperty(ParameterList parameters, String value) {
-            LastModified property = new LastModified(parameters, value);
-            return property;
-        }
-    }
-}
diff --git a/src/main/java/net/fortuna/ical4j/extensions/property/Uid.java b/src/main/java/net/fortuna/ical4j/extensions/property/Uid.java
deleted file mode 100644
index 7941858..0000000
--- a/src/main/java/net/fortuna/ical4j/extensions/property/Uid.java
+++ /dev/null
@@ -1,55 +0,0 @@
-package net.fortuna.ical4j.extensions.property;
-
-import net.fortuna.ical4j.model.*;
-import net.fortuna.ical4j.validate.ValidationException;
-
-/**
- * Created by fortuna on 11/09/15.
- */
-public class Uid extends Property {
-
-    private static final long serialVersionUID = 1L;
-
-    public static final String PROPERTY_NAME = "UID";
-
-    private String value;
-
-    public Uid() {
-        super(PROPERTY_NAME, PropertyFactoryImpl.getInstance());
-    }
-
-    public Uid(ParameterList params, String value) {
-        super(PROPERTY_NAME, params, PropertyFactoryImpl.getInstance());
-        setValue(value);
-    }
-
-    @Override
-    public void setValue(String aValue) {
-        this.value = aValue;
-    }
-
-    @Override
-    public void validate() throws ValidationException {
-
-    }
-
-    @Override
-    public String getValue() {
-        return value;
-    }
-
-    public static class Factory extends Content.Factory implements PropertyFactory<Uid> {
-        public Factory() {
-            super(PROPERTY_NAME);
-        }
-
-        public Uid createProperty() {
-            return new Uid();
-        }
-
-        public Uid createProperty(ParameterList parameters, String value) {
-            Uid property = new Uid(parameters, value);
-            return property;
-        }
-    }
-}
diff --git a/src/main/java/net/fortuna/ical4j/extensions/property/Url.java b/src/main/java/net/fortuna/ical4j/extensions/property/Url.java
deleted file mode 100644
index 3915790..0000000
--- a/src/main/java/net/fortuna/ical4j/extensions/property/Url.java
+++ /dev/null
@@ -1,54 +0,0 @@
-package net.fortuna.ical4j.extensions.property;
-
-import net.fortuna.ical4j.model.*;
-
-/**
- * Created by fortuna on 11/09/15.
- */
-public class Url extends Property {
-
-    private static final long serialVersionUID = 1L;
-
-    public static final String PROPERTY_NAME = "URL";
-
-    private String value;
-
-    public Url() {
-        super(PROPERTY_NAME, PropertyFactoryImpl.getInstance());
-    }
-
-    public Url(ParameterList params, String value) {
-        super(PROPERTY_NAME, params, PropertyFactoryImpl.getInstance());
-        setValue(value);
-    }
-
-    @Override
-    public void setValue(String aValue) {
-        this.value = aValue;
-    }
-
-    @Override
-    public void validate() throws ValidationException {
-
-    }
-
-    @Override
-    public String getValue() {
-        return value;
-    }
-
-    public static class Factory extends Content.Factory implements PropertyFactory<Url> {
-        public Factory() {
-            super(PROPERTY_NAME);
-        }
-
-        public Url createProperty() {
-            return new Url();
-        }
-
-        public Url createProperty(ParameterList parameters, String value) {
-            Url property = new Url(parameters, value);
-            return property;
-        }
-    }
-}
diff --git a/src/main/resources/META-INF/services/net.fortuna.ical4j.model.PropertyFactory b/src/main/resources/META-INF/services/net.fortuna.ical4j.model.PropertyFactory
index 4017ef4..ce31ed3 100644
--- a/src/main/resources/META-INF/services/net.fortuna.ical4j.model.PropertyFactory
+++ b/src/main/resources/META-INF/services/net.fortuna.ical4j.model.PropertyFactory
@@ -7,17 +7,13 @@ net.fortuna.ical4j.extensions.property.WrRelCalId$Factory
 net.fortuna.ical4j.extensions.property.WrTimezone$Factory
 
 # calext extensions
-net.fortuna.ical4j.extensions.property.Categories$Factory
 net.fortuna.ical4j.extensions.property.Color$Factory
 net.fortuna.ical4j.extensions.property.Conference$Factory
-net.fortuna.ical4j.extensions.property.Description$Factory
 net.fortuna.ical4j.extensions.property.Image$Factory
-net.fortuna.ical4j.extensions.property.LastModified$Factory
 net.fortuna.ical4j.extensions.property.Name$Factory
 net.fortuna.ical4j.extensions.property.RefreshInterval$Factory
 net.fortuna.ical4j.extensions.property.Source$Factory
 net.fortuna.ical4j.extensions.property.Uid$Factory
-net.fortuna.ical4j.extensions.property.Url$Factory
 
 # CalDAV
 net.fortuna.ical4j.extensions.caldav.property.Acknowledged$Factory