Fenix Li-ion 21700 3.6 V Mah Rechargeable Battery With Usb Ports And Protection Circuits New . 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. Specifications for Fenix Li-ion 21700 3.6 V 5000 Mah Rechargeable Battery With Usb Ports And Protection Circuits New: Manufacturer: Fenix Battery Quantity: 1 Battery Type: 21700 Battery Chemistry: Lithium-Ion Package Contents: Fenix Li-ion 21700 3.6 V 5000 Mah Rechargeable Battery With Usb Ports And Protection Circuits New