Usage Tips:Feature: - High Precision - Racing look enhance the characteristic to your car/vehicle - Fitment : Universal 52mm diameter Voltmeter fit for Motorcycle Car /Truck/ Gasoline Engine (The compatibility just for reference .Please make sure the item fit for your car before purchase.) Fitment: Fit most of 12Volt gasoline vehicle, Fit 2" or 52mm Diameter Gauge Pods holder Application: Color:Black Voltage:DC 12V Diameter:52mm/2 Material:Plastic Quantity: 1 Set Connection: The white line is at heater ab Black line signal line C, gray line signal ground D The green wire of the instrument is connected with the black wire of the sensor. The gray line is connected to the negative pole of the battery. One white wire connect with the car shell or battery negative pole. Another white wire connect to the ACC line of ignition switch The white line is the heater and does not distinguish between positive and negative electrodes About the air fuel gauge, please see the installation instructions. Please select the correct SKU when purchasing, as shown in the picture for the package's product Package Included: as the picture shows 1x Air Fuel Ratio Gauge Package Included: as the picture shows 1x Air Fuel Ratio Gauge 1x Sensor Package Included: as the picture shows 1x Sensor OR 1x Gauge Cup