Aero Precision M4E1 AR15 Complete Upper, 223 Remington/556NATO, 16 Barrel, 1:7 Twist, ATLAS S-ONE Handguard, Mid Length Gas System, Cerakote Finish, Flat Dark Earth, Does Not Include BCG or Charging Handle APAR700315M7 This complete upper includes the 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. The 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.