Our AR15 .223/5.56 Bull barrel thread protector should fit all standard .936 barrels with a standard 1/2"-28 that are factory threaded for a flash hider. This protector can be used in place of your muzzle brake, flash hider, or suppressor so your barrel won't get damaged when not in use. Made of 416R Stainless steel construction with a matte finish. Includes a crush washer.