MARINE WHITE ATV 4x4 TRUCK BOAT CAR POWER BOAT COMPASS BRACKET MOUNT - FIVE OCEANS-------------------------------------------------------------------------------Bracket Mount Compass This compass series can be used on cars, trucks, atv, 4x4, fast runabouts, bass boats, center consoles and sport boats. Bracket mount type, white case. Features include built-in compensator magnets. Fast response and precision engineeringEasy to read precision dialWaterproof, durable and long lasting, corrosion resistantEasy to mount and remove Extra Sensitive Compensation SystemMaterial: PlasticColor: White Size: 5-1/8" x 3-1/16" diam (130 x 78 mm)Total Width including bracket: 4-1/3" (110mm)All Magnetic Compasses are vulnerable to magnetic interference, which will produce errors, called deviation. It is the Owner/Operator and/or Helmsman"s responsibility to make sure the compass is properly installed and compensated. Compensation is the act of correcting for deviation. Magnets (speakers, microphones etc.), ferrous metals (steel, iron, etc.) and current carrying devices are common causes of deviation. It is important to understand that magnetic compasses point toward Magnetic North. There is a difference between Magnetic North and True North, and that difference is called variation. Variation differs depending on your geographical location and can be determined by referring to a local chart.