Aluminum: Our AR-15/M4/M16 magazines go above and well beyond the industry standard. With the use of cutting-edge robotic manufacturing technology, and our commitment to construct our magazines with only the highest quality USA materials, you are guaranteed a high-quality result. Our lightweight aluminum magazines are manufactured 100% start to finish in the USA using 6061 grade aluminum, heat treated to a condition of T6, and hard-coat anodized per MIL-A-8625 Type III class I. The result is a dependable, long lasting magazine that Functions flawlessly. There's a reason why these have been in military service for decades! Assembly components: 6061 Aluminum Body, heat treated to T6 Condition, Hard Anodized per MIL-A-8625 Type III Chrome Silicon Springs Mil-Spec Polymer Followers - Available in Black, Green, Orange, or Grey 6061 Aluminum Floor plate Hard Andozide per MIL-A-8625 Type III, dyed Black