Zenport APG60 Zen-Tek Ammonia Gas Pressure Gauge, 60 PSI NH3 Ammonia filled 0-60 psi pressure gauge 2.5-inch (63.5mm) diameter stainless steel case and bezel, polycarbonate window Stainless steel .25-inch national pipe thread bottom connection and internals Grade A accuracy of 1.6% full range High visibility dial face and numbers