Relief Valves are Proportional Not Pop Type Safety Valves, Not Preset Field AdjustableKnurled Adjustment Screw and Locked with Jam NutPressure Range: 0-27 HgSet Pressure Tolerances: 3% of Set PressureTemperature Range: -65F to 250FConstruction: C360 Machined Brass Body, Stainless Steel Spring, Nylon Piston and Nitrile Seal (PCVR-04 Stainless Steel Piston and Seal).Bubble Tight to Within 5 psig for Set Pressure 50 psig or Less, Bubble Tight to Within 10% for Set Pressures Greater than 50 psig. 100% Testing or 2.5 AQL Sample Testing, Conforming to AP1 527.Everseal 483 Sealant Standard.