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. A matching topcoated NiB-X charging handle is a perfect complement for this upper receiver.