Product Filter Product Filter: Category -- Choose -- Search HVAC/Refrigeration Gauges Marsh Instruments has offered the widest variety of gauges and thermometers for HVAC and refrigeration applications for over 155 years. Whether commercial, industrial, or residential, Marsh Instruments has the instruments to meet your HVAC/R needs. G33 Series - Gas Test Gauge Gas Pressure Test Kit Heating System/Altitude Gauge Manifold Gauge - Blue Gauge Serviceman's Test Gauge W01 Series, Ammonia Gauge W04 Series - Contractor Gauge Water Test Gauge/Hose Gauge REQUEST