The Brownells Short Muzzle Brakes offer an effective braking solution, with minimal added length Features: Designed to provide maximum braking ability in the smallest size possible One inch overall length Two rows of 0.125" ports evenly distribute exiting gasses and pressure Wrench flats on each side for simple installation Available with a 1.00" OD for perfect fitting to AR-15 or precision rifle barrels 1.00" OD models feature 5/8-24 threads Mfg: Brownells SPECS: Length - 1". Diameter - 1.0". Threads - 5/8-24. Do not use bullets larger in diameter than .30/7.62 in SMB 7.62 (unless exit port is opened).