M4E1 Enhanced Upper Receiver finished in Purple Anodized. Comes assembled with port door (dust cover) and forward assist installed. Includes barrel nut and barrel nut wrench. Features M4 Feedramps and .250 takedown pin holes. Handguard mounting platform is forged into the receiver and it is compatible with Aero Precision Enhanced and Quantum Series handguards, and most BAR-system handguards. Will support barrels with a diameter up to 1 inch. Not piston-kit compatible.