Liquid-filled Fire Apparatus Panel Gauges are commonly used for discharge line pressure. FEATURES OF FIRE APPARATUS PANEL GAUGES Zytel nylon case ½” blow out plug Bright stainless steel bezel material Black bezel option ¼” Male NPT brass center back connection Kem-X freeze proof protection Phosphor bronze, filled with freeze proof liquid - isolated by diaphragm Acrylic lens Fill Fluid: Low temp glycerin (for -40°F - 150°F service) 2-½” or 3-½” aluminum dial; two sided baked enamel finish Accuracy: 1 % Full Scale - ANSI Grade 1A