This M4 Profile Crowned Barreled Upper Assembly is complete and ready to snap onto your Lower. The highly accurate 4150 Chrome Moly Vanadium steel barrel is chrome lined and rifled 1 x 9″ Right Hand twist. The muzzle is finished with a plain crown to comply with legal restrictions in States where threaded muzzles and flash hiders are prohibited. A standard A2 Front Sight is fitted – the bayonet lug has been machined off. The aluminum flat top Upper Receiver is complete with Bolt Carrier Assembly, Charging Handle, Forward Assist, Ejection Port Cover, and Removable A4 Carry Handle with 300 – 600 meter Dual Aperture Rear Sight.