The AR-STONER(TM) Linear Muzzle Brake is an effective option for directing sound and escaping gas toward the muzzle and away from the shooter of AR rifles. This heat-treated steel, linear muzzle break has a phosphate finish and features six vents surrounding the exit hole. It is pre-drilled for pin and weld installation and allows you to configure your rifle for your next trip to the range or field.NoteCrush washer recommended but not included