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 – ATLAS R-ONE Handguard of choice – 14.5 5.56 Mid-Length CMV Barrel – Low Profile Gas Block and Mid Length Gas Tube – VG6 Precision GAMMA 556 SL (pinned and welded) – 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 for optional attachments – 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 – 14.5 5.56 Mid-Length Barrel Features: – Chamber: 5.56 – Length: 14.5 – Twist: 1 in 7 – Threading: 1/2×28 – Material: Chrome Moly Vanadium – Finish: QPQ corrosion resistant finish both inside and out – Gas Block: .750 – Gas Port: .0785 – Gas System Length: Mid – Weight: 26oz – M4 Barrel Extension – HP and MPI Tested