Complete upper receiver with colt carrier group and charging handle: M4 parkerized 4150 chrome vanadium barrel, chambered in 5.56 with a 1:8 twist Birdcage flash hider Carbine length gas system 15" m-lok handguard Flat-top mil-spec upper receiver with installed dust cover and forward assist Black Nitride Bolt Carrier Group Mil-spec standard charging handle Mate this to your complete mil-spec lower receiver. Install some sights and go shoot.