This AR15 Complete Upper is the same upper receiver used in our AERO M16A4 Special Edition Complete Rifle and features a 20 5.56 Barrel w/ Pinned FSB A2 Handguard and A2 Detachable Carry Handle. – Upper Features: – Upper: Standard M4 Upper Receiver – Barrel: 20 5.56 NATO Rifle Length 1:7 Twist 4150 Chrome Moly Vanadium QPQ corrosion resistant finish – Sights: A2 Detachable Carry Handle and A2 Front Sight Block w/ Bayonet Lug – Handguard: A2 Style Handguard Rifle Length – Gas System: Rifle Length Gas System – Muzzle Device: Standard A2 Flash Hider