diff --git a/urchin/urdf.py b/urchin/urdf.py
index 582a183..43a7e93 100644
--- a/urchin/urdf.py
+++ b/urchin/urdf.py
@@ -438,7 +438,7 @@ def copy(self, prefix="", scale=None):
         """
         if scale is None:
             scale = 1.0
-        b = Box(
+        b = self.__class__(
             size=self.size.copy() * scale,
         )
         return b
@@ -517,12 +517,12 @@ def copy(self, prefix="", scale=None):
                 raise ValueError(
                     "Cannot rescale cylinder geometry with asymmetry in x/y"
                 )
-            c = Cylinder(
+            c = self.__class__(
                 radius=self.radius * scale[0],
                 length=self.length * scale[2],
             )
         else:
-            c = Cylinder(
+            c = self.__class__(
                 radius=self.radius * scale,
                 length=self.length * scale,
             )
@@ -588,7 +588,7 @@ def copy(self, prefix="", scale=None):
             if scale[0] != scale[1] or scale[0] != scale[2]:
                 raise ValueError("Spheres do not support non-uniform scaling!")
             scale = scale[0]
-        s = Sphere(
+        s = self.__class__(
             radius=self.radius * scale,
         )
         return s
@@ -706,7 +706,7 @@ def _from_xml(cls, node, path, lazy_load_meshes):
         kwargs["meshes"] = meshes
         kwargs["combine"] = combine
 
-        return Mesh(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         # Get the filename
@@ -735,7 +735,7 @@ def copy(self, prefix="", scale=None):
 
         Returns
         -------
-        :class:`.Sphere`
+        :class:`.Mesh`
             A deep copy.
         """
         meshes = [m.copy() for m in self.meshes]
@@ -749,7 +749,7 @@ def copy(self, prefix="", scale=None):
                 meshes[i] = m.apply_transform(sm)
         base, fn = os.path.split(self.filename)
         fn = "{}{}".format(prefix, self.filename)
-        m = Mesh(
+        m = self.__class__(
             filename=os.path.join(base, fn),
             combine=self.combine,
             scale=(self.scale.copy() if self.scale is not None else None),
@@ -872,7 +872,7 @@ def copy(self, prefix="", scale=None):
         :class:`.Geometry`
             A deep copy.
         """
-        v = Geometry(
+        v = self.__class__(
             box=(self.box.copy(prefix=prefix, scale=scale) if self.box else None),
             cylinder=(
                 self.cylinder.copy(prefix=prefix, scale=scale)
@@ -941,7 +941,7 @@ def _from_xml(cls, node, path):
         fn = get_filename(path, kwargs["filename"])
         kwargs["image"] = PIL.Image.open(fn)
 
-        return Texture(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         # Save the image
@@ -963,7 +963,7 @@ def copy(self, prefix="", scale=None):
         :class:`.Texture`
             A deep copy.
         """
-        v = Texture(filename=self.filename, image=self.image.copy())
+        v = self.__class__(filename=self.filename, image=self.image.copy())
         return v
 
 
@@ -1041,7 +1041,7 @@ def _from_xml(cls, node, path):
             color = np.fromstring(color.attrib["rgba"], sep=" ", dtype=np.float64)
         kwargs["color"] = color
 
-        return Material(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         # Simplify materials by collecting them at the top level.
@@ -1073,7 +1073,7 @@ def copy(self, prefix="", scale=None):
         :class:`.Material`
             A deep copy of the material.
         """
-        return Material(
+        return self.__class__(
             name="{}{}".format(prefix, self.name),
             color=self.color,
             texture=self.texture,
@@ -1140,7 +1140,7 @@ def origin(self, value):
     def _from_xml(cls, node, path, lazy_load_meshes):
         kwargs = cls._parse(node, path, lazy_load_meshes)
         kwargs["origin"] = parse_origin(node)
-        return Collision(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         node = self._unparse(path)
@@ -1165,7 +1165,7 @@ def copy(self, prefix="", scale=None):
             if not isinstance(scale, (list, np.ndarray)):
                 scale = np.repeat(scale, 3)
             origin[:3, 3] *= scale
-        return Collision(
+        return self.__class__(
             name="{}{}".format(prefix, self.name),
             origin=origin,
             geometry=self.geometry.copy(prefix=prefix, scale=scale),
@@ -1248,7 +1248,7 @@ def material(self, value):
     def _from_xml(cls, node, path, lazy_load_meshes):
         kwargs = cls._parse(node, path, lazy_load_meshes)
         kwargs["origin"] = parse_origin(node)
-        return Visual(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         node = self._unparse(path)
@@ -1273,7 +1273,7 @@ def copy(self, prefix="", scale=None):
             if not isinstance(scale, (list, np.ndarray)):
                 scale = np.repeat(scale, 3)
             origin[:3, 3] *= scale
-        return Visual(
+        return self.__class__(
             geometry=self.geometry.copy(prefix=prefix, scale=scale),
             name="{}{}".format(prefix, self.name),
             origin=origin,
@@ -1344,7 +1344,7 @@ def _from_xml(cls, node, path):
         yz = float(n.attrib["iyz"])
         zz = float(n.attrib["izz"])
         inertia = np.array([[xx, xy, xz], [xy, yy, yz], [xz, yz, zz]], dtype=np.float64)
-        return Inertial(mass=mass, inertia=inertia, origin=origin)
+        return cls(mass=mass, inertia=inertia, origin=origin)
 
     def _to_xml(self, parent, path):
         node = ET.Element("inertial")
@@ -1381,7 +1381,7 @@ def copy(self, prefix="", mass=None, origin=None, inertia=None):
             origin = self.origin.copy()
         if inertia is None:
             inertia = self.inertia.copy()
-        return Inertial(
+        return self.__class__(
             mass=mass,
             inertia=inertia,
             origin=origin,
@@ -1448,7 +1448,7 @@ def copy(self, prefix="", scale=None):
         :class:`.JointCalibration`
             A deep copy of the visual.
         """
-        return JointCalibration(
+        return self.__class__(
             rising=self.rising,
             falling=self.falling,
         )
@@ -1512,7 +1512,7 @@ def copy(self, prefix="", scale=None):
         :class:`.JointDynamics`
             A deep copy of the visual.
         """
-        return JointDynamics(
+        return self.__class__(
             damping=self.damping,
             friction=self.friction,
         )
@@ -1601,7 +1601,7 @@ def copy(self, prefix="", scale=None):
         :class:`.JointLimit`
             A deep copy of the visual.
         """
-        return JointLimit(
+        return self.__class__(
             effort=self.effort,
             velocity=self.velocity,
             lower=self.lower,
@@ -1686,7 +1686,7 @@ def copy(self, prefix="", scale=None):
         :class:`.JointMimic`
             A deep copy of the joint mimic.
         """
-        return JointMimic(
+        return self.__class__(
             joint="{}{}".format(prefix, self.joint),
             multiplier=self.multiplier,
             offset=self.offset,
@@ -1789,7 +1789,7 @@ def copy(self, prefix="", scale=None):
         :class:`.SafetyController`
             A deep copy of the visual.
         """
-        return SafetyController(
+        return self.__class__(
             k_velocity=self.k_velocity,
             k_position=self.k_position,
             soft_lower_limit=self.soft_lower_limit,
@@ -1872,7 +1872,7 @@ def _from_xml(cls, node, path):
         if len(hi) > 0:
             hi = [h.text for h in hi]
         kwargs["hardwareInterfaces"] = hi
-        return Actuator(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         node = self._unparse(path)
@@ -1900,7 +1900,7 @@ def copy(self, prefix="", scale=None):
         :class:`.Actuator`
             A deep copy of the visual.
         """
-        return Actuator(
+        return self.__class__(
             name="{}{}".format(prefix, self.name),
             mechanicalReduction=self.mechanicalReduction,
             hardwareInterfaces=self.hardwareInterfaces.copy(),
@@ -1958,7 +1958,7 @@ def _from_xml(cls, node, path):
         if len(hi) > 0:
             hi = [h.text for h in hi]
         kwargs["hardwareInterfaces"] = hi
-        return TransmissionJoint(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         node = self._unparse(path)
@@ -1982,7 +1982,7 @@ def copy(self, prefix="", scale=None):
         :class:`.TransmissionJoint`
             A deep copy.
         """
-        return TransmissionJoint(
+        return self.__class__(
             name="{}{}".format(prefix, self.name),
             hardwareInterfaces=self.hardwareInterfaces.copy(),
         )
@@ -2083,7 +2083,7 @@ def _from_xml(cls, node, path):
         if trans_type is None:
             trans_type = node.find("type").text
         kwargs["trans_type"] = trans_type
-        return Transmission(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         node = self._unparse(path)
@@ -2105,7 +2105,7 @@ def copy(self, prefix="", scale=None):
         :class:`.Transmission`
             A deep copy.
         """
-        return Transmission(
+        return self.__class__(
             name="{}{}".format(prefix, self.name),
             trans_type=self.trans_type,
             joints=[j.copy(prefix) for j in self.joints],
@@ -2476,7 +2476,7 @@ def _from_xml(cls, node, path):
             axis = np.fromstring(axis.attrib["xyz"], sep=" ")
         kwargs["axis"] = axis
         kwargs["origin"] = parse_origin(node)
-        return Joint(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         node = self._unparse(path)
@@ -2553,7 +2553,7 @@ def copy(self, prefix="", scale=None):
             if not isinstance(scale, (list, np.ndarray)):
                 scale = np.repeat(scale, 3)
             origin[:3, 3] *= scale
-        cpy = Joint(
+        cpy = self.__class__(
             name="{}{}".format(prefix, self.name),
             joint_type=self.joint_type,
             parent="{}{}".format(prefix, self.parent),
@@ -2720,7 +2720,7 @@ def copy(self, prefix="", scale=None, collision_only=False):
         if not collision_only:
             visuals = [v.copy(prefix=prefix, scale=scale) for v in self.visuals]
 
-        cpy = Link(
+        cpy = self.__class__(
             name="{}{}".format(prefix, self.name),
             inertial=inertial,
             visuals=visuals,
@@ -3728,7 +3728,7 @@ def copy(self, name=None, prefix="", scale=None, collision_only=False):
         copy : :class:`.URDF`
             The copied URDF.
         """
-        return URDF(
+        return self.__class__(
             name=(name if name else self.name),
             links=[v.copy(prefix, scale, collision_only) for v in self.links],
             joints=[v.copy(prefix, scale) for v in self.joints],
@@ -3818,7 +3818,7 @@ def join(self, other, link, origin=None, name=None, prefix=""):
             )
         )
 
-        return URDF(
+        return self.__class__(
             name=name,
             links=links,
             joints=joints,
@@ -4091,7 +4091,7 @@ def _from_xml(cls, node, path, lazy_load_meshes):
 
         data = ET.tostring(extra_xml_node)
         kwargs["other_xml"] = data
-        return URDF(**kwargs)
+        return cls(**kwargs)
 
     def _to_xml(self, parent, path):
         node = self._unparse(path)