Features: Made of durable material, this battery case is built to last and features an Led display for monitoring battery capacity, voltage, and current. Designed for anyone in need of a reliable power solution, this battery case can be easily assembled with 4x18650 batteries. In addition to charging your devices, this battery case also includes an hand warmer function, making it versatile for winter. 18650 batteries are not included in the package, you need to purchase separately. Can only use the 18650 battery of which positive electrode is flat top. Removable design, simply install the battery into the slot and correctly connect the connector to build a complete power bank. Maintaining and replacing batteries becomes very easy. If a battery malfunctions or needs to be replaced, you only need to open the sleeve and replace the corresponding battery, without the need for complex welding operations. Specifications: Material:Plastic Color:Black,Red1,Blue,Green;(Optional) Number of batteries: 4x18650 batteries Size:Approx.103x80x24mm/4.06x3.15x0.94in Double USB Output:5V/2.1A (Most) Input:Type-C/Micro USB Package Includes: 1x Power Bank Case (Battery not include) note: Please allow 1-2cm errors due to manual measurement,please make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item.