This complete upper includes our ATLAS R-ONE Handguard! The R-ONE handguards are designed with size and weight in mind while still providing plenty of real-estate to accommodate any attachment needs the end user may have. Our proprietary ATLAS attachment system is a durable and dependable mounting platform maintaining a slim profile while still providing the strength and stability customers have grown to love from Aero Precision handguards. – Includes: – M4E1 Threaded Assembled Upper Receiver – 12.7 ATLAS R-ONE Handguard of choice – 13.9 5.56 Mid-Length CMV Barrel – Low Profile Gas Block and Mid-Length Gas Tube – Product comes assembled – This complete upper does not include BCG or Charging Handle. – M4E1 Threaded Upper Receiver Features: – New enhanced forging that gives the upper receiver a billet look – New picatinny profile that blends seamlessly with our Enhanced Series Handguards – M4 Feedramps – .250 takedown pin holes – Laser engraved T-marks – Includes port door and forward assist installed – ATLAS R-ONE Handguard Features: – Full top picatinny rail – Quick disconnect sling socket at the 3 6 and 9 o’clock positions – Compatible with low profile gas blocks – 1.3 Inside diameter – 1.5 Outside diameter – Compatible with mil-spec AR15 upper receivers and barrels – 13.9 5.56 M4 CMV Barrel Mid-Length Features: – 5.56 Nato 13.9 Barrel 1/7 twist 4150 CrMoV QPQ gas port drilled – .750 gas block journal – Mid-Length Gas System – M4 Feed Ramp Extension – HP and MPI tested – Standard A2 flash hider