About this item [ How to connect wires ? ] Red wire connect to 9-32VDC; Blue wire connect to Ground(-); Orange wire connect to Blacklight [ How to install it ? ] Open a hole of 52mm (2 1/16″) in the panel and allow a clearance of 70mm (2 3/4”) behind the panel to fit the gauge. Put the gauge in the hole and screw down. [ Widely used ] Suitable for all cars, tractors, vans, vessels, boats, yachts, etc. IP68 Waterproof. Could work underwater 1M. [ Back Light ] 7 different backlight adjustable. Red, Green, Blue, White , Yellow, Grass, Orange, Purple, Auto