This is 0.28″ 5 Wires Red Led Digital Dual DC 100V 10A Ammeter  Voltmeter. This meter will measure up to 100 VDC with a 0.1-volt resolution.

One thing to note is, this meter has 2 wiring harnesses. One harness is to provide power for the meters, that’s the 2 poles with a RED and a BLACK lead. Small size, portable, the magnitudes of voltage and current are displayed on the same screen at the same time.

This can be supplied anywhere from 6 volts DC up to 30 VDC. This is a separate power supply that is isolated from the source, it is possible to use the same supply but it seems to affect the amp meter reading. The 3 wire harness is used for a ground that connects directly to the battery or supply ground of the load