The single-piece, monolithic upper on this Colt CR6940 AR-15 Semi-Automatic Rifle is often under appreciated. The idea behind on monolithic upper allows for zero rail shift between the rail and upper receiver. As one solid piece, no impact shift can take place. Only torque shift. This gives you extra confidence in your sighting devices being properly zeroed, even after field use. Perfect for IR lasers and back-up iron sights. This Colt 6940 features mil-spec furniture with an M4 profile barrel. The flip-up front sight/gas block is a nice feature that can tuck away until you need it. It's hard to beat a Colt. With the monolithic upper receiver, this is about as tough as a Colt can get. 1-piece monolithic rail/upper A2 grip Collapsible stock Magpul MBUS flip-up rear sight Flip-up front sight/gas block M4 profile barrel 1:7 twist rate A2 flash hider