Made of a unique high-tech injection molded plastic, this Fobus mag pouch offers a fit that is impossible to duplicate with leather or other materials. It offers security and comfort with unbelievable retention. Lightweight and impervious to hot or cold weather, it will provide a lifetime of maintenance-free use.The term "double stack" refers to the way the bullets fit inside the magazine that fits inside the case. In this instance, one double stack magazine fits in this case..