The new 21700 battery from Fenix can handle twice the power of a standard 18650 battery. The additional mAh's allow flashlights like the PD36R and TK22 to have 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. Currently, the Fenix 5000U 21700 battery is compatible with the Fenix PD36R, TK22 V2.0, and TK22UE. Compatible chargers include the Fenix ARE-A2, A4, D1, and D2. Fenix plans to continue developing flashlights that are compatible with the 21700 batteries.