Not all AR magazines are created equal and the Okay Industries SureFeed magazines are some of the best when it comes to aluminum mags. With over 40 years of battle tested use, these aluminum magazines are preferred by soldiers in various areas of the U.S. Military. With a four-way, anti-tilt, self-lubricating follower, you can rely on this 30 round (pinned to 5) 5.56 magazine to feed correctly without any issue no matter the condition. The stainless-steel spring provides proper tension and keeps rounds properly aligned for optimal function. These USGI magazines are all hardcoat anodized and this model features a grey dry-lube finish. Every SureFeed magazine is put through a multi-step inspection and testing process to ensure they live up to the performance standards that people have come to know with Okay Industries. Features: 30 round (pinned to 5) Aluminum AR-15 magazine Hardcoat anodized with a Mil-Spec Grey finish Four-way, anti-tilt, self-lubricating follower Mil-Spec stainless steel follower spring Each magazine passes a rigorous inspection and testing process 100% made in the U.S.A. While polymer magazines do have their benefits and space age aesthetic, aluminum mags are not to be forgotten about. One of the benefits that aluminum has over polymer is that it does not swell or shatter in extremely high or low temperatures. The aluminum feed lips are also strong enough to withstand the pressure of a fully loaded magazine over long periods of time without bending or breaking. The history of Okay Industries goes back to WWII where they helped manufacture millions of M1 Carbine magazines for the United States Military. Fast forward and they helped co-develop the 30-round (pinned to 5) M16 magazine and has been a preferred supplier of magazines to the U.S. government ever since. Now Okay Industries are making their widely popular AR-15 magazines available to the public with the SureFeed and SureFeed E2 designs.