This is a battery level meter with two USB ports. In addition to displaying the battery level, you can also charge devices using the USB ports. It also has a switch, allowing you to turn it on and off as needed. The default setting is for lithium iron phosphate batteries, but it can also be changed to lead-acid batteries or lithium-ion batteries. The voltage can also be changed to your desired voltage. Remove the back cover and long-press the white button. You can change the settings while it's flashing by pressing the button. (Long-press again while flashing to change the voltage) L: Lithium-ion battery (12, 16, 20, 24V, etc.) P: Lead-acid battery (12, 24, 36, 48V, etc.) F: Lithium iron phosphate battery (10.5, 14, 17.5, 21V, etc.) Batteries are not included. The photos are examples of use. The case of this product is made with a 3D printer. Please understand that there may be layer lines and minor scratches. The material is ABS. The terminal holes are 8.4mm.