Ruger Radial Muzzle Brake, 223REM/556NATO, Black Finish 90486 This .223 Rem / 5.56 NATO Radial Port Muzzle Brake muzzle brake's design reduces felt recoil and muzzle movement. It is made from alloy steel with a black oxide finish to complement most firearms. Installs with a 11/16" open end wrench or crescent wrench.