Aero Precision APAR700315M8: This complete upper includes Aero Precision\'s new ATLAS S-ONE Handguard! The S-ONE line of handguards are designed with size and weight in mind, providing the perfect addition to your lightweight build. Aero Precision\'s 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. This complete upper does not include BCG or Charging Handle. Includes: M4E1 Threaded Assembled Upper Receiver 15\" ATLAS S-ONE Handguard 18\" 5.56 Rifle Length CMV Barrel Low Profile Gas Block and Rifle Length Gas Tube Product comes assembled 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 S-ONE Handguard Features: Front and rear picatinny rail Eliminated center of top rail for weight reduction Indexing grooves in 12:00 position for positive grip control 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 18\" 5.56 Rifle Length Barrel Features: 5.56 Nato 18\" Rifle Length Barrel 4150 CrMoV w/ QPQ finish 1/7 twist .750 gas block journal Rifle length gas system M4 Feed Ramp Extension HP and MPI tested Standard A2 flash hider