Feature: 1. This product has the function of voltage display and USB output (mobile phone charging). There are only two wiring, which is simple. It can be used for DC power supply in the voltage range of 8-40v or 12V and 24V batteries. The two USB ports can output 5V 2A (maximum) and automatically distribute the output current. 2. This product is designed with universal size (48 * 29mm) and installed with square hole direct snap, with strong universality. Specification: Display resolution: (DC8-40v) 0.01V when less than 10V and 0.1V when greater than 10V Display mode: three digit 0.28"LED nixie tube Display color: Red / Green / Blue Refresh speed: About 200ms / time USB output: 5V2A (maximum current 2A, two USB automatic distribution) Input: 8-40v (available for 12V and 24V batteries) Operating temperature: - 10 ~ 65 Overall dimension: 48 * 29mm Opening size: 46 * 27mm Lead length: 20cm Tips: 1. 40V is the limit input voltage of this product. Do not exceed this voltage when using. In particular, it should be noted that the reverse electromotive force generated by the motor or relay, switch, etc. in the circuit will be superimposed on the power supply voltage, causing permanent damage to the product; 2. This product is not waterproof and dustproof. Attention should be paid to waterproof, moisture-proof, dustproof and shockproof in use. Note: Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you! Please allow 1-2cm measuring deviation due to manual measurement. 1 xDigital Voltmeter