MERCURY has been meticulously engineered for the .223/5.56 caliber to provide superior recoil reduction and neutralize muzzle rise with a smooth, balanced release of blast energy. Progressive 90 side ports vent combusting gases at intervals that spread out the recoil impulse for efficient, accurate follow-up shots. Like all Ultradyne muzzle devices, a timing nut is included for easy installation. Features: 1/2-28 thread pitch 416 stainless steel Nitride finish Includes timing nut