Polished brass construction & brass wetted material Polycarbonate window 1/4" NPT thread low mounting 2 1/2" diameter 0 - 4000 PSI range Ametek U.S. Gauge Model P-601 Compressed Gas Pressure Gauge. Perfect for use on a wide range of regulators. High pressure gauges are used for measuring cylinder or tank pressure, while low pressure gauges are used on the downstream side of the regulator to indicate regulated, reduced pressure. This gauge is both UL 404 listed and in accordance with Level IV of ASME B40, 100-2005.