Chesapeake White SS 4″ Speedometer – 60MPH (Pitot)Perimeter-lighted White dial with stylish Blue and White graphics, polished stainless steel bezel, contoured White pointer and domed glass lens.Electronic speedometers operate by capturing pulses produced by a sensor. the pulses are then electronically converted to a speed reading very much like a tachometer converts ignition pulses to RPM.Pitot tube type speedometers operate by pressure from the water being forced into the pitot tube. This pressure is then transmitted through flexible tubing to the bourdon tube movement inside the speedometer head where it is converted into a speed reading by the movement mechanism. Pitot tube sold separately.4″ – Hole Size: 3.375″ (85mm)Specifications:Anti-scratch glass lens12 VDC negative groundCan be adapted for 24 VDC systemsDual Scale – Imperial and MetricFactory P/N SE9521*Sold as an Individual**Gauge Cover not IncludedThis product may not be returned to the original point of purchase. Please contact the manufacturer directly with any issues or concerns.