Aero Precision APRH200024: This 9mm chambered 11 inch straight profile barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish and 1/2-28 x .400 full profile threads. Designed to work with both Colt/RR and Glock style AR builds Compatible with EPC upper receivers, as well as standard mil-spec upper receivers 9mm on an AR15 platform operates by blowback and does not need a gas block or gas tube Threaded 1/2x28 to give you versatility when choosing a muzzle device Integrated barrel extension Since the \"barrel extension\" is an integral part of the barrel, the length stated is the true overall length. For example, an 11\" 9mm barrel has the same outer dimensions/length as a 10.5\" 5.56 barrel. IMPORTANT: A standard 1/2x28 flash hider will not have enough clearance for a 9mm round to pass. Before installing a muzzle device, ensure a 9mm round will drop freely through the muzzle device bore.