The Billet-AR upper receiver set is 100% machined in the USA and was engineered from the ground up to address structural design weaknesses in standard USGI receivers and enhance overall tolerances. It has a precise bolt raceway for smoother chambering, more rigid receiver walls to reduce firing flex. The Billet-AR upper receiver is CNC machined from 7075-T6 aerospace aluminum billet stock with a top Picatinny rail, M4-style extended feed ramps, and smooth side profile without forward assist for maximum accuracy potential. NOTE: Requires a dust cover, forward assist, charging handle, barrel, handguard, gas block, muzzle device, gas tube and BCG (Bolt Carrier Group) to complete.