This is a factory 22-round magazine for MP5-style GSG-5/522 rimfire firearms. Heckler & Koch’s iconic MP5 is one of the most popular and successful submachine guns in history—with a proven track record & unique design—and the GSG-5/522 delivers the same finish and feel; with affordable rimfire ammo and trustworthy factory magazines … These tough, German-made polymer stick magazines feature a full 22-round capacity, easy-to-use reloading button, wide-cut witness slot and durable steel spring internals. They’re compatible with all models of GSG-5/522, GSG-5PK, and SD models.