Euro White 2" Water Temperature Gauge (100-250F)Perimeter-lighted White dial with bold Black graphics, Black aluminum bezel, contoured White pointer and flat glass lens.A temperature gauge operates by sending a low amperage current through the gauge's meter to ground via a sending unit with variable resistance. The resistance of the sending units increase or decrease with the changes in pressure, temperature, etc...As the sender's resistance varies, the amount of current allowed to flow through it to ground changes and the meter deflects, showing the temperature.2" - Hole Size: 2.0625" (53mm)Specifications:. Anti-scratch glass lens. Perimeter-lighted White dial. 12 VDC negative ground. Can be adapted for 24 VDC systems. Dual Scale - Metric and Imperial. Factory P/N GP9119*Sold as an Individual**Gauge Cover not Included