This 21700 battery from Fenix is designed to handle the additional power and capacity for high lumen flashlights giving them longer run times. What makes this 21700 battery even better is the USB Type-C charging port that is embedded in the cell. You don't have to use a separate charger to charge the battery; it can all be done with a wall adapter and USB Type-C charging cord. It is likely that you already have these in your home since many cellphones use this same type of charging port.

Shipping Note: Lithium ion batteries are considered "dangerous goods" per US transportation regulations and can often only be transported via ground shipment. Orders containing loose batteries will typically take much longer than predicted to be delivered. Delivery times of 14+ days are not uncommon.