This Gemtech .45 UMP can was made with an UZI mount instead of the HK UMP flange mount.  The UZI mount is designed to use an UZI barrel that is cut down about 1/2″ in front of the barrel flange for a more compact setup.  

The original UMP can used aluminum baffles and was not serviceable.  

After filling the can up with crud, I had Curtis Tactical re-core it to be fully serviceable out of 17-4 SS.