These incredible 75rd drum magazines are manufactured to fit AR-15 platform rifles and pistols chambered in 7.62X39. These are the rear load style 75 round drum magazines. The rear loaders are the most popular for a couple of reasons. First, they are based on the original military design and function and feed flawlessly. Also, unlike other drums, which are cumbersome to load due to being fed from the top one at a time, these drums load quickly. Simply open the rear cover and drop the rounds in. They can also be stored fully loaded with no pressure on the springs. Then, when you are ready to use it, simply wind the spring using the winding key, snap it in the rifle, and you are ready to go.