.223 Rem 20" Bull barrel is made of 416 stainless steel and comes with a single-rail aluminum gas block. Features a target crowned muzzle, button-rifled barrel with 1:9" twist and six right-hand grooves, and a sandblasted matte gray finish. This barrel has M4 style feedramps and a rifle length gas system. It is designed to be used with a free floating handguard.