This upper offers a 12.5" Ballistic Advantage 4150 Chrome Moly QPQ barrel a 1:7 RH military twist rate. The Flash hider is a A2 this is for PISTOL OR SBR USE ONLY. It is also made of chrome-moly steel and HP tested. Our barrels are Mil-Spec or better. The upper is our Mil-spec flat top with M4 ramps. We recommend a 55gr or 62gr bullet for best accuracy. The front sight is a A2 F-Marked with bayonet lug.