For testing, inspection or critical production processes. They are calibrated on a high accuracy manometer. A serial number and certification of accuracy are supplied. (N.I.S.T. traceble) This gauge combines accuracy with rugged construction, accuracy + or - 0.5% of span. Valve adaptors are available under accessories. They are available in 0 - 30 in hg.*Comes with brass toggle valve and test report, traceable to N.I.S.T. Rugged Plano lockable gun security, foam padded carry case, Also made in USA.