Euro Black 4 Tachometer - 4000 RPM (Diesel) (Mechanical Takeoff & Var Ratio Alt) 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 ingition system alternator tach signal generator or magnetic pickup sender. The tach is hooked up to +12VDC Ground and one of the signal sources listed above. 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 Plastic Cases for corrosion resistance and long life Perimeter-lighted Black dial Can be adapted for 24 VDC systems Factory P/N TD9122 *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. Specifications: Gauge Type: Tachometer - Diesel Series: Euro Black Voltage - Input Range (Volts): 12/24 V Gauge Size: 4 Box Set: No Box Dimensions: 5 H x 6 W x 6 L WT: 0.7 lbs UPC: 759266328426 Quick Guide (pdf)