Faria Chesapeake Black SS 4"" GPS Speedometer w/Digital Depth Display - 6 0MPH - Transducer Required4""- Hole Size: 3.375"" (85mm)The GPS Speedometer is a drop in replacement for your current speedometer to match your existing instrument dash.GPS information is gathered from an internal GPS antenna. No external antenna required. The Faria GPS Speedometer uses a highly accurate 48 channel GPS receiver. You can be sure that the Faria GPS Speedometer is giving you the most accurate GPS information available on the market today.Course Over Ground (COG) and actual heading (compass heading over ground) are displayed on the optional digital LCD.Speed data is shown by an analog pointer. This pointer is driven by a digital stepper motor for increased accuracy and minimized pointer bounce during vessel operation.Benefits:No external GPS antenna requiredPremium LED back-lit dialsUltra fast Satellite acquisition time (TTFF) 1 second from Hot startSpeed Accuracy of +/- 1 MPHHeading Accuracy of +/- 1 DegreeDigital stepper motor driven pointersIdeal replacement for speed sensing devices (pitot tube and paddle wheel) that fail over timePerfect for slow moving vessels where pitot tubes just don't workDeutsch connectors