Angstadt Arms complete upper receiver pistol assembly is ready to run out of the box with any 9mm AR-15 lower receiver. Featuring the same high quality parts that go into their UDP-9 pistol, this completed upper receiver is compatible with both GLOCK(R) and COLT(R) style 9mm magazines. Complete 9mm upper receiver pistol assembly with 6″ barrel and 5.5″ hand guard. Ready to run with any 9mm AR-15 dedicated lower receiver.