This is a "like new" Centurion Arms CM4 11.5" 5.56 Upper Receiver group. It has under 100 rounds through it. I have never cleaned this upper receiver and you can see in the images how little carbon there is even in the chamber. Looking for $499 or best offer. -- Centurion Arms CM4 5.56mm 11.5" Hammer Forged Carbine Barrel 1 in 7in twist extra thick chrome lining and barrel steel specifically engineered for machine guns for longer life (most all hammer forged barrels on the market are not made of this steel). -- Upper receiver is standard forged Mil-Spec with M4 Extended feed ramps -- Centurion Arms Low Pro .750 Gas Block -- 10.5in MLOK CMR Rail --Carbine gas tube -- Standard A2 Flash Hider -- Polished Feed Ramps