Houston pressure gauges are all stainless steel industrial gauges (case, mechanism, tube and process connection) with glycerine filled for high pressure and precision measurement, Psi scale 0-30 Psi up to 40,000 Psi, can be used in chemical processing, instrumentation controls, oil fields, paper plants, agricultural plants, water and waste water Cases are 2.5″ & 4″ stainless steel, 1/4″ NPT, 1/2″ NPT & 1/4″ HP-9/16-18 UNF connection, lens tempered glass. Quartz- USA pressure gauges in made in USA