The Spikes Tactical Generation 2 Billet Upper Receiver offers precision-machined construction for AR-15 builds chambered for .223 Remington/5.56 NATO with mil-spec barrel nut threading.Spikes Tactical Generation 2 Billet Upper ReceiverPrecision CNC machined from billet aluminumCompatible with .223 Remington and 5.56 NATO cartridgesMil-spec barrel nut threading for standard compatibilityBlack anodized finish for durabilitySKU: SFT52B2Ideal for custom AR-15 builds requiring high-quality upper receivers with reliable mil-spec compatibility and versatile caliber options for both sporting and tactical applications.