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