Open a 3-3/8 inch dimension and 2-3/4 inch depth hole, put gauge into it and fasten.Hook up easily, 3 wires connection(power, ground, lighting). This is complete unit, can work directly with gps sensor together, not need other sensor cables. Mount the sensor at any position, on or under the dashboard.It takes about 30 seconds to get signal in the first time, but less than 3 seconds after that. It gets quicker under a clear view of the sky. Sometimes if signal is missing, pls. reconnect all wires and restart it.It shows current speed and odometer(cannot be reset), no trip meter.CNSPEED Speedometer Less power consumption, longer life, higher precision,quick location confirmation, short start up time.Speedometer: 220Km/hVoltage: 12V/24VApplicable models: UniversalColour: As shownMaterial: ABS+metalSize: 75mmx90mmx85mmPackage Contents:1 * 220Km/h Speedmeter1 * Chinese and English manual1 * Multi-plug socketOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.