Specifications:Item Type: TachometerMaterial: AlumInium Alloy+ABSDiameter: Approx. 52mm/2inFitment: For Automobile, outboard engine, construction machinery, motorcycleConnection Mode:Black: Power negative (-)Red: 9-30 VDCBlue: RPM signalYellow: BacklitWhite: AdjustmentInstruction:1. The white line touches the negative pole for 3 seconds to enter the setting speed ratio mode.If you leave the negative pole for more than 3 seconds,it will exit the setting mode.2. When the white wire touches the negative pole,the value keeps increasing ;when the white wire is loosened and touches the negative pole,the value keeps decreasing.The longer the white line touches the negative pole,the faster teh value counts.The minimum step value of counting is 0.1,the adjustable range is 1.0-360.3. After adjusting the speed ratio to meet your requirements,the white line leaves the negative pole.After 3 seconds,the tachometer will automatically save the result you set.If the settings do not meet your requirements,reset them.Package Included:1 x Tachometer1 x Manual