"Sea Marine Compass Illuminated pivoting compass Wired for 12 Volt red illumination Visible Lubber Line With Adjustable Mounting Bracket Adjustable Sun Visor Individually balanced dials for Precision Fast Response and precision Engineering Corrosion Resistant Waterproof, durable and long lasting Built in Accuracy compensators Windshield or Dash Mount Easy to read precision dial With Mounting screw slot Suitable for Watercraft, Boat, Caravan and Truck To adjust Locate the slotted compensator. Adjust knobs at the middle and side of the base When received, the factory preset knobs should be in neutral (horizontal) position To exert maximum eject on compensators, turn knob 900 to positive (vertical) position"