ar Water Temperature Gauge 2 Inch for 12 Volt System Universal Condtion: Air-core meter moverment. Suitable for 12 volt systems. Mounting directly in 2 inch hole. Scale from 100F to 250 F,40 ℃ to 120 ℃. 2 inch water temperature gauge with backlight. Come with black metal panel and 'U" bracket for add-on or replacement purpose. It can alert you that higher or lower than normal water temperature reading,to protect your driving safe. How to Connect: Red wire lead for + volt supply to internal lamp Black wire to system ground S Threaded terminal for connecting sensor wire + Threaded terminal for connecting + volt supply - Threaded terminal for connecting system ground Pls remember that the sensor is automatically connected to system ground when installed. If installing where the body of the sensor is not tied to system ground, it will be necessary to hook up a ground to the body of the sensor element. Note: Hole diameter is 2 inch. Meter OD is 2 3/16 inch. Meter depth from front of panel to the end of the mounting studs is 2 inch. All you will need is 18 gauge stranded wire to make the necessary connections. Package Included: 1 X Water Temperature Gauge 1 X Sensor 1 X Manual