Product specifications: 1/4" male NPT pipe thread Center/back installation 0-6Bar 2.3" Face A new 0-6bar back mounted water pressure gauge. The gauge has a 2.3 inch surface and a 1/4 inch NPT thread in the center of the rear of the meter. This is a brand new barometer. The meter can be used to measure air, water, oil, gas and any material that is non-corrosive to brass. This is a chrome-plated steel bezel with a chrome-plated steel bezel.