Efest Battery case 20700/21700. Great way to store your spare set of 20700/21700 Batteries that are not being used. It also makes an awesome travel case.
Note: Use a battery case for transportation - it is crucial to always carry your extra batteries in a case and not to leave them loose in your bag or pockets. If batteries encounter metal objects such as coins or keys, a hazardous explosion can occur as the interaction can complete a circuit between a positive and a negative.