2.5" (63mm) to 6" (150mm) durable gauges 2.5" (63mm) dial have a blue and red coloured case for easy identification Dual scale (psi/°F) Flutterless movement on the 2.5" (63mm) Chlorofluorocarbon (CFC) temperature scales (R-12, R-22 & R-502) Brass internals 1/4" NPT standard CRN registered