Designed to direct muzzle blast away from shooters. Which is especially helpful on short barreled rifles and pistols. Machined from 6061 aircraft grade aluminum billet and hardcoat anodized. 3.25 inches long and 1.2 inches in diameter. Note: All S.D. .40S&W barrels are threaded with .45 CAL threads (.578-28) to accept .45 CAL muzzle devices. Features: Comes with crush washer. 6061 aircraft grade aluminum. Hard-coat anodized. Sturdy construction. Light weight construction. Made in U.S.A. .45 CAL Threaded .578-28