Euro Black 4 Tachometer - 7 000 RPM (Gas - All Outboard) Perimeter-lighted Black dial with bold white graphics black aluminum bezel contoured white pointer and flat glass lens. Electronic tachometers work by counting pulses generated by the ignition system alternator tach signal generator or magnetic pickup sender. The tach is hooked up to +12VDC Ground and one of the signal sources listed. By selecting the right tach and setting the switch on the back to the correct position you let the tachometer know how many pulses are sent per each engine revolution. 4 - Hole size: 3.375 (85mm) Specifications: Anti-scratch glass lens 12 VDC negative ground Can be adapted for 24 VDC systems Factory P/N TC9011 Manufacturer : Faria Beede Instruments Manufacturer Part No : 32805 UPC : 759266328051