Euro Black 2 Digital Hourmeter Gauge Perimeter-lighted Black dial with bold White graphics, Black aluminum bezel, contoured White pointer and flat glass lens.Hourmeter operates by applying battery voltage across the gauges register motor to ground. The register increments increase when the key switch in on. Route power through a normally open Oil Pressure switch to count engine running hours.2 - Hole size 2.0625 53mmSpecificationsAnti-scratch glass lens12 VDC negative groundCan be adapted for 24