Faria Beede Instruments Euro Black 4" Tachometer w/Hourmeter - 6000 RPM Gas - Inboard. 375" (85mm) Electronic tachometers work by counting pulses generated by the ingition system alternator tach signal generator or magnetic pickup sender. The tach is hooked up to +12VDC Ground and one of hte signal sources listed above. By selecting the right tach and setting the switch on the back to the correct postion you let the tachometer know how many pulses are sent per each engine revolution. Benefits: Wide range of scales Multiple signal sources Rugged Reliable construction 7 character LCD display 0-999999.9 Hours Updates in .1 increments Specifications for Faria Beede Instruments Euro Black 4" Tachometer w/Hourmeter: Manufacturer: Faria Beede Instruments Color: Black Features of Faria Beede Instruments Euro Black 4" Tachometer w/Hourmeter Wide range of scales Available for gas or diesel engines Multiple signal sources Rugged Reliable construction 4" - Hole size: 3.375" (85mm) Package Contents: Faria Beede Instruments Euro Black 4" Tachometer w/Hourmeter Faria Beede Instruments 32832: Euro Black 4" Tachometer w/Hourmeter - 6000 RPM Gas - Inboard