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: 1/2x28 - 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