Chesapeake White SS 4″ Tachometer with Hourmeter – 6000 RPM (Gas) (Inboard)Perimeter-lighted White dial with stylish Blue and White graphics, polished stainless steel bezel, contoured White pointer and domed 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 lensPerimeter lighted back light12 VDC negative groundCan be adapted for 24 VDC systemsTechnical Specifications:7 character LCD display0-999999.9 HoursUpdates in .1 incrementsFactory P/N TC9128*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.