The M-4756-3 is a 0-300 PSI liquid filled pressure gauge that has a front O.D. of 2 7/16", glass face diameter of 1 3/8", back steel case fits a hole size of 1 9/16" O.D.. This gauge is a flange mount with 3 - 1/8" holes on the flange for mounting and an 1/8" NPT threaded connection on the back. (Image shown is a 0-200 PSI Liquid Filled Pressure Gauge.)