Type-C Charging: With wired charging jack. It can be charged here and there with a type-c charger; USB-C charging brings more convenience. Compact and lightweight portability; Great spare battery when you go camping or other outdoor activities About Protection: There are current overload protection, leakage protection, over charge protection and over current pretection can be assured to use Compatible with: BF-888S/BF-88A/H-888S/BF-666S/BF-777S/BF-999S/H-777/AR-5/PX-888S/TW-888/BF-88ST Model: BL-1 Voltage: DC3.7V Charger Limit Voltage: DC4.2V Power: 5.5Wh Compatible with: BF-888S/BF-88A/H-888S/BF-666S/BF-777S/BF-999S/H-777/AR-5/PX-888S/TW-888/BF-88ST