[2 Connection Methods]3 wires are connected separately to measure voltage and power(Red yellow is both for pos, black is ); 3 wires are used as 2 wires, connected to measure voltage(Red and Yellow can be paired for pos, black is ) [Features]Reverse polarity protection, voltmeter 't burn out if reverse polarity is applied; high ; low starting working voltage; fine adjustment function [Mini DC Voltmeters]Total 10PCS, 4 colors combined(2PCS Red/Yellow/Blue/Green/White); 0.28 inch LED Panel; small in size and light in weight; wire is made of 28awg gauge; install the hole: 23*10 mm [Note]Max voltage with yellow and red connected is 40V.To measure 40V (up to 100V) the yellow wire is connected to a separate voltage source that is 40V or less, Weight: 0.1212542441 pounds, Manufacturer: Kueohse