WMD Guns AR-15 A3/A4 Upper Receiver Forged w/M4 Feed Ramps NiB-X Black. 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. Specifications for WMD Guns AR-15 NiB-X Complete Upper Receiver: Manufacturer: WMD Guns Muzzle Device: No Finish: NiB-X Fabric/Material: 7075-T6 Aluminum Gun Type: Rifle Gun Make: AR Platform Gun Model: AR-15 Package Contents: WMD Guns AR-15 NiB-X Complete Upper Receiver What firearm models does the manufacturer say WMD Guns AR-15 NiB-X Complete Upper Receiver is compatible with? The manufacturer says that WMD Guns AR-15 NiB-X Complete Upper Receiver is compatible with AR-15WMD Guns 1-NIBXURF-Black: AR-15 A3/A4 Upper Receiver Forged w/M4 Feed Ramps NiB-X Black