This upper offers a 1:7 RH military twist rate. It is made of 4150 chrome-moly steel with chrome lining and HP tested.  The upper is Mil-spec and at a length of 14.5″ it’s pretty darn short. A A2 flash hider is the default flash hider. We recommend a 55gr or 62gr bullet for best accuracy. The front sight is a A2 with bayonet lug.