This is a Spike's Tactical Lower/Upper Set known as the Upper/Lower Receiver chambered in 223 Remington, model STS1512.
If you are looking for a set to build your next rifle on" look no further. Spike's uppers and lowers are made to the highest industry standards and will be the perfect foundation for your build.
Features:
FDE Cerakote Upper/Lower Set
7075 T6 Construction
Multi Caliber