This muzzle brake's radial-port design reduces felt recoil and muzzle movement. Made from 4140 chrome molly steel with a black oxide finish to complement most firearms. Installs with a ¾" open end wrench or crescent wrench. Torque the brake to 15-20 ft-lbs. - no crush washers are required. It fits rifles with ½" x 28 threads chambered in .350 Legend including the AR-556® MPR and the Ruger American® Rifle Ranch and the PC Carbine™ chambered in 9mm. Dimensions: 1-3/4" length, .8" diameter. Weight: 2.0 oz. ounces. Made in the USA by Pemmco.