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. M4E1 Threaded Assembled Upper Receiver Choice of 12" or 15" M-LOK ATLAS S-ONE Handguard 16" 5.56 Mid CMV Barrel, 18" Rifle Barrel Low Profile Gas Block and Mid-Length/Rifle Length Gas Tube Dependi Mfg: Aero Precision