The Colt AR-15/M4 Magazine is a standard factory replacement magazine. This magazine is for AR-15 models chambered in .223 Remington or 5.56 NATO and holds 20 rounds of ammunition. The magazine body is made from high quality aluminum and features a gray finish. This particular version of the magazine features an aluminum base plate with a black finish. The magazine is made by Colt so you can be certain that the magazine meets the specifications and tolerances set forth by the factory using the same manufacturing process and materials as the magazines which originally shipped with your pistol. You can rest easy with the knowledge that the magazines you are purchasing will fit and perform optimally.