The NiteCore Multi-purpose Portable Battery Magazine is a battery holder with enough room for four 21700 batteries. The holder, however, also has room to store, for instance, liquid bottles or nozzles (with a diameter of 23 mm). The holder is made from rubber to make sure you can easily add the batteries. With the included velcro you can easily secure the whole and with the loop you can hang the battery holder from your belt or bag. The casing absorbs shocks to make sure it can withstand quite a lot. In addition, this NiteCore battery holder is made from sustainable material.