The Model 475-000-FM Mark III handheld digital manometer from Dwyer Instruments, Inc. (Michigan City, IN) measures positive, negative, and differential pressures of air or natural gas in the low range of 0 to 1.00 in. wc. Features include accuracies up to +0.5% F.S., a zero-adjust knob, dual-sized connections that accommodate 1/8 in. or 3/16 in. vinyl or rubber tubing, and instructions printed on the instrument's back.