WMD Guns AR-15 A3/A4 Upper Receiver Forged w/M4 Feed Ramps Stripped NiB-X NRA Blue 1-NIBXUF-NRA Blue. Ideal building block for a long lasting AR15. This 7075 T6 Aluminum forged Mil Spec stripped 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. NiB-X is almost twice as hard as anodize and has a much lower coefficient of friction. Topcoated on the outside only with a ceramic color coating leaving NiB-X exposed on the inside wear surfaces. Standard colors are available. A matching topcoated NiB-X charging handle is a perfect complement for this upper receiver. Specifications for WMD Guns AR-15 Stripped NiB-X Complete Upper Receiver: Manufacturer: WMD Guns Finish: NiB-X Gun Make: AR Platform Gun Model: AR-15 Condition: New Package Contents: WMD Guns AR-15 Stripped NiB-X Complete Upper Receiver What firearm models does the manufacturer say WMD Guns AR-15 Stripped NiB-X Complete Upper Receiver is compatible with? The manufacturer suggests that WMD Guns AR-15 Stripped NiB-X Complete Upper Receiver is compatible with AR-15WMD Guns 1-NIBXUF-NRA Blue: AR-15 A3/A4 Upper Receiver Forged w/M4 Feed Ramps Stripped NiB-X NRA Blue