Fits into a mounting hole of 85 mm diameter with a 70 mm depth; insert the gauge and fasten securely. Wiring and power: 3wire connection (power, ground, lighting). This is a complete unit and can work directly with a GPS sensor, no additional sensor cables required. Mounting flexibility: Can be mounted at any position, on or under the dashboard. Display with GPS data: Shows Current Speed; TRIP or COG (choose one); ODO (cannot be reset). Backlight options: Red, Green, Blue, White, Yellow, Orange, Purple, Light Green, or automatic. Use case 1: Install in a passenger car dashboard to monitor realtime speed and mileage using GPS data, without needing extra sensors. Use case 2: Equip a fleet vehicle to track mileage with a nonresettable ODO, while keeping the unit mounted under the dashboard for space efficiency. Use case 3: Install in a vehicle with limited dashboard space by mounting the unit in a convenient location; select from multiple backlight colors or automatic mode for day/night readability.