NiB-X A3/A4 Upper Receiver w/M4 Feed Ramps, Forged, 7075 T6 Mil Spec forging with M4 feed ramps. Built out with a NiB-X ejection port cover door and forward assist. Ideal building block for a long lasting AR15. This 7075 T6 Aluminum forged Mil Spec receiver with M4 feed ramps has NiB-X coating inside and out to provide an exceptionally tough, ultra-smooth surface finish for outstanding wear resistance and lubricity. Add an NiB-X charging handle to compete the receiver.