The Dwyer 1223-36-W/M is a Series 1223 Flex-Tube U-Tube Manometer. It combines the inherent accuracy of the “U” Tube with the durability of tough, long-lasting plastic construction. The columns are made of 0.375˝ O.D. flexible and shatterproof clear butyrate tubing and are backed by a white scale channel to provide maximum color contrast. Scales are extruded high impact polystyrene plastic, formed to hold columns in perfect alignment. Stark white scales have graduations and numbers silkscreen-printed in black for maximum legibility. Suitable for total pressures to 100 psi, determine velocity and static pressures, leakage, fan and blower efficiency, filter resistance, and gas pressures.