The YHM Flat Top Upper Receiver is made from 7075-T6 aluminum (Forged) and has a hardcoat anodized matte black finish. It features M4 Style feed ramps and T Markings and the inside is coated with dry film lube. It accepts standard upper receiver parts (dust covers, forward assists, etc.) and Mil-Spec lower receivers. It will fit and function with your standard lower receiver. NOTE: Requires a dust cover, forward assist, charging handle, barrel, handguard, gas block, muzzle device, gas tube and BCG (Bolt Carrier Group) to complete.