Dwyer 2002 Magnehelic Differential Pressure Gauge, Type, 0 to 2" WC;

The magnahelic gauge is the industry standard to measure fan and blower pressures, filter resistance, air velocity, furnace draft, pressure drop across orifice plates, liquid levels with bubbler systems, and pressures in fluid amplifier or fluidic systems. The gauge's motion is Damped with high-viscosity silicone fluid. The zero adjustment screw is conveniently located in the plastic cover, and is accessible without removing the cover. O-Ring seal provides pressure tightness. Rugged design resists shock, vibration, and overpressure. The helix is precision-made from an alloy of high magnetic permeability. Mounted in jeweled bearings, it turns freely, following the magnetic field to move the pointer across the scale. The samarium cobalt magnet is mounted at one end of the range spring and rotates the helix without mechanical linkages. What's included: two 1/8 inch NPT plugs, two 1/8 inch rubber tubing adapters, and three mounting adapters with screws the industry standard in indicating low air or gas pressures of positive, negative, or differential pressures large, easy-to-read 4 inch (102 mm) dial no manometer fluid to evaporate, freeze, or cause toxic or leveling problems.