This magazine was originally designed for use by the RPK, the squad automatic version of the AK. Exactly of the same design as the Steel 30 Round Double Stack Ribbed Magazine except that it is longer and can hold 10 more rounds. There are two types of these magazines available. The first is a genuine 40 round magazine, usually of Chinese origin (as pictured above) that functions flawlessly. The second type is actually a 30 round magazine cut in half and welded onto the bottom of another 30 round magazine. These usually look ugly because of the obvious weld and SOME may not function properly.