Euro Black 2" Water Pressure Gauge (30 PSI)Perimeter-lighted Black dial with bold White graphics, Black aluminum bezel, contoured White pointer and flat glass lens.A pressure gauge operates by sending a low amperage current through the gauges&'; 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: Anti-scratch glass lens Plastic Cases for corrosion resistance and long life Can be adapted for 24 VDC systems Dual Scale - Imperial and Metric Factory P/N OP1004*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: Water Pressure Series: Euro Black Voltage - Input Range (Volts): 12/24 V Gauge Size: 2" Box Set: No Box Dimensions: 5"H x 6"W x 6"L WT: 0.7 lbs UPC: 759266128101 Quick Guide (pdf)