The OP/TECH USA Battery Holster keeps you shooting when a battery dies. This convenient, American-made holster can hold a standard-size DSLR battery, 3 AA batteries, or others of similar dimensions. It is not designed to accommodate larger pro DSLR batteries, such as the Nikon EN-EL18a. A hook-and-loop closure ensures that your power source stays put until it's needed. And what makes the holster great is the fact that it easily slides onto a camera strap or belt for quick retrieval when you need power immediately.