This machined, flash hider is 5.5" in length but only gives an AR-15 9mm about 2" in length. Threaded 1/2x36, coated in black oxide. This device slides over the barrel providing a clean look while protecting the barrel and the threads. The muzzle help to force the signature and muzzle blast at least 2" from the end of the barrel without sacrificing performance. Barrel must be .74" or thinner to fit inside. Outside diameter is 1".