Lordosis Of The Spine Faria Chesapeake White SS 4" Speedometer 60MPH (Pitot). 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 lens 12 VDC negative ground Can be adapted for 24 VDC systems Dual Scale Imperial and Metric Factory P N SE9521 *Sold as an Individual **Gauge Cover not Included This product may not be returned to the original point of purchase. Please contact the manufacturer directly with any issues or concerns.