Next Level Prime Billet AR15 Upper Receiver Model closeout- The Prime uppers fit nicely on any AR15 mil-spec lower receiver. Machined from solid block aluminum and hard coat anodized. We have discontinued the Prime series, so if you are looking for an upper receiver to start a build, this is a great deal for a billet upper! Since the Prime series is discontinued, so we do not have any more Prime Lower receivers to create a set. Each NLX Prime billet AR15 upper receiver starts with a solid USA Milled 7075 Aerospace Alloy Aluminum block. We cut to length on our Programmable CNC Marvel Saw. After cutting, we perform lathe operations on live tooling Mazak Machines. We then transfer machining to our New Haas SS mills with Touch probe Capabilities. Once completed, we hard coat anodize to mil-spec tolerances ensuring a durable finish.