This is a professional bracket mount compass that is corrosion resistant which can be mounted on your windshield or dash Mount. Easy to read precision dial and can be used for almost any vehicle or boat. Ideal for keen travelers who want to take their preferred vehicle on a trip. Compass is equipped with a No.37 Light Bulb (12V) Dimensions Approx: 15cm x 10cm x 9cm Illumination The two leads from the compass light may be connected to the light switch of regular electrical system of the boat. Some prefer including a small rheostat to regulate the level of brightness. In making the installation. Both Wires should be twisted around each other to prevent setting up a disturbing magnetic field. Switches or rheostats should be located at least 300mm from the compass.