Colt's Manufacturing Complete Upper Receiver, Fits AR, 223 Remington/5.56 NATO, 14.5" Chrome Lined Barrel, 1:7 RH Twist, Magpul Flip-Up Rear Sight, M4 Contour Barrel, Standard Sling Swivel, Bolt Carrier Assembly and Charging Handle, Black Finish, Not Pinned and Welded LE6921CK