This is an Arms Tech upper in excellent condition with less than 200 rounds thru it. It has a vortex flash hider, flattop receiver and gas block, no sights, m4 style handguard, forward assist and comes with a matching bolt, no carrier. It also has a 1 in 9" gain twist. It stabilized 75 gr. Hornady TAP ammo just fine and is very accurate. I fired 5 mags thru it in full auto and never had a problem. $610 shipped.