Ruger Radial Port Muzzle Brake 223 Rem5.56 NATO 1/2-28 Tpi 1.75 Black. 56 NATO 1/2"-28 tpi 1.75" Black O - Ruger's .223 Rem/5.56 NATO Radial Port Muzzle Brake muzzle brake's design reduces felt recoil and muzzle movement. Installs with a 11/16" open end wrench or crescent wrench. Torque the brake to 15-20 ft-lbs no crush washers are required. This brake is compatible with AR-556 rifles and other .223 Rem/5.56 NATO caliber firearms with 1/2"-28 muzzle threads. Specifications for Ruger 90486 Radial Port Muzzle Brake 223 Rem5.56 NATO 1/2"-28 Tpi 1.75" Black O: Manufacturer: Ruger Finish: Black Oxide Fabric/Material: Alloy Steel Condition: New Package Contents: Ruger 90486 Radial Port Muzzle Brake 223 Rem5.56 NATO 1/2"-28 Tpi 1.75" Black O Ruger 90486 Radial Port Muzzle Brake 223 Rem5.56 NATO 1/2-28 Tpi 1.75 Black