AAC 9mm Barrel for Glock 17, 13.5x1LH Nitrided With Thread Protector. Now available from Advanced Armament Corps, threaded pistols barrels. This barrel will fit your Glock 17 in 9mm, and has M13.5x1 Left Hand threads. Thus allowing a direct thread suppressor to be used. Made with AAC's renowned quality in materials and workmanship, this barrel is second to none.