The Dwyer Instruments 490A-4-HKIT Wet/Wet Manometer with Hydronic Meter Kit is a digital pressure-measuring instrument designed for HVAC hydronic systems. It works by sensing pressure through connected hoses and displaying accurate pressure or differential pressure readings from 0 to 100 PSI. This versatile kit is suitable for hydronic boilers, pumps, valves, chillers, heat exchangers... https://www.partshnc.com/dwyer-instruments-490a-4-hkit-wet-wet-manometer-w-hydronic-meter-kit-0-100-psi