Coral 2" Water Pressure Gauge (30 PSI)Perimeter-lighted Black dial with stylish White and Blue graphics, Black aluminum bezel with burnished leading edge, contoured White pointer, and flat glass lens.A pressure 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 change in pressure.2" - Hole Size: 2.0625" (53mm)Specifications:Scratch Resistant LensBlack Aluminum BezelContoured White PointerDual Scale - Metric and ImperialFactory P/N OP1000*Sold as an Individual**Gauge Cover not Included