NiB-X A3/A4 Upper Receiver w/M4 Feed Ramps, Forged, 7075 T6 Mil Spec forging with M4 feed ramps.  Built out with a topcoated 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.  A ceramic color topcoat is then applied to the outside of the receiver only.  Leaving the inside wear resistant and lubricious.  Add an NiB-X charging handle and NiB-X bolt carrier group to compete the upper receiver.