Zenport Zen-Tek Instruments liquid glycerin filled 100 PSI pressure gauge is an excellent choice for vibrating environments, such as around working machinery and is built with a 2. 5-inch diameter ABS case with 372 plastic window, 1/4 NPT brass bottom connection and brass internal mechanism. Glycerin helps prevent icing and moisture penetration. This gauge is great for use with water systems, air tanks, oil systems and more. This quality gauge features grade A accuracy (1. 6%) and features a high visibility dial and number readout.