The BLACKOUT® flash suppressor is the most efficient design available. The proprietary features eliminate muzzle flash, even on CQB-length barrels. The BLACKOUT® is inherently stronger and more impact resistant than four prong designs, while not being subject to the rapid erosion of closed-ended units. A high strength corrosion-resistant aerospace alloy, and ultra-hard Nitride finish provide the highest level of durability. Military tested and selected. There are two different options for 5/8-24, a deep and standard socket. Deep socket is for .75" barrels and smaller(profile behind the threads) and the standard socket fits all profiles.