The Vltor Modular Upper Receiver (MUR) is a unique AR-15 Flat-Top upper receiver that undergoes a rigorous quality control procedure during manufacture to ensure a precise, strong and consistent product that will serve the shooter for a lifetime. Vltor CNC-Machines the 7075 Aluminum Forging only after it has been fully stress relieved, and then heat and cryogenically treated. Each upper is finished by hand and all critical dimensions inspected, and finally given a protective Type III, Class 2 Hard Anodized Finish.