GPS Controlled speedometers utilize state of the art satellite guidance to achieve unsurpassed accuracy. - Special features: By utilizing the toggle switch you can alternate to different modes such as: MPH, Knots, Digital compass, Tachometer and Volts. - Epoxy encapsulated to protect from harmfull vibrations and harsh saltwater elements. - Front sealed - 3 3/8" cutout. - No pitot tube required - High speed memory recall