Feature: 1. Convenient Charging: You can charge your phone no matter where you are, no more limitation from fixed power source. Suitable for 21700 battery, also compatible with 18650/18700/20700 batteries 2. Single Battery Available: The inner battery box can contain 2 batteries, but only 1 battery loaded can make the power bank work, providing a satisfying using experience. 3. Protection Function: Built in chip has overvoltage and overcurrent protection, taking full care of the safety of your mobile phone and battery. 4. Portable Type: When traveling, you can carry the DIY power bank in your pocket, bag, briefcase or suitcase to mobile phone charging at any time. 5. Wide Application: Suitable for mobile phones, and can also be used for MP3, MP4, digital camera, tablet computer and other products by different cables. DC 5V universal power supply. Specification: Item Type: DIY Power Bank Material: ABS Model: H02B Application: For Mobile Phone Battery Type: 21700 Battery x 2(Not Included); Also Compatible With 18650/18700/20700 Batteries (Not Included) Weight: Approx. 69g / 2.4oz Output Port: USB 5V 2A Input Port: Micro/Type-C 5V 2A Scope Of Application: Support All Types Of Mobile Phone Charging. Package List: 1 x DIY Power Bank Case Note: It's just an empty shell, can be used as a power bank after batteries are plugged.