Dwyer, 1223-M400-D, U-tube manometer, range 200-0-200 mm w.c.These inexpensive manometers measure positive, negative and differential pressures. Dwyer® Flex-Tube® U-Tube Manometers combine the inherent accuracy of the simple "U" Tube with the durability of tough, long-lasting plastic construction. Columns are of .375" O.D. flexible and shatter proof clear butyrate tubing. They are easily accessible for cleaning. Indicating tube is backed by 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.Range 400mm water/mercury suitable for total pressures to 100 psi - for determining velocity and static pressures, leakage, fan and blower efficiency, filter resistance, and gas pressures. Ideal wherever a portable, direct reading manometer is needed.FeaturesMinor Divisions of 2 mm water column are silkscreened in jet black on stark white scale for positive definition. Easy to read, even at a distance, they are acrylic coated for permanence. Furnished with one 3/4 ounce bottle of red gage fluid.Our simplest, lowest cost basic U-gage. A dependable U-tube manometer that withstands hard use and provides accurate, high visibility readings. For use with water, mercury or red gage fluid. For mercury filled manometers, a scale clamp bar, Dwyer® Part No. A-363 is recommended. One pair of carrying plugs and a pair of non-kink vinyl tube connectors are included with each manometer.Standard Accessories Magnetic mounting clips; tube clamp and Type "a" connectionsconsisting of two rapid shut off molded nylon tubing connectors; two 1/8" pipethread to tube adapters; two 3-foot lengths of Tygon® plastic tubing.