Dwyer Flex-Tube Series 1222 U-Tube Manometer, 8-0-8"WC using Red Gauge Fluid U-tube manometer with red or green color concentrate measures positive, negative, and differential pressure for determining velocity and static pressures, leakage, fan and blower efficiency, filter resistance, and gas pressures Columns composed of 1/8" outside diameter flexible and shatterproof clear butyrate tubing for use with water, red fluid, or mercury (sold separately) Choice of calibration in inH2O or mmH2O using water for use with fluorescein green concentrate or mercury (sold separately), or red gauge fluid Choice of measuring range with 1/10 inH2O (2mmH2O on metric units) graduations silkscreened in jet black on stark white scale to ease reading Includes one bottle of red or green gauge fluid