Faria Beede Instruments Euro Black 4" Speedometer - 80MPH Mechanical. 375" (85mm) 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. Benefits: Wide range of speeds Rugged Reliable construction Specifications for Faria Beede Instruments Euro Black 4" Speedometer: Manufacturer: Faria Beede Instruments Color: Black Additional Features: Mechanical Length: 4 in Features of Faria Beede Instruments Euro Black 4" Speedometer Black aluminum bezel Bold white graphics Contoured white pointer Flat glass lens Package Contents: Faria Beede Instruments Euro Black 4" Speedometer Faria Beede Instruments 32812: Euro Black 4" Speedometer - 80MPH Mechanical