FOR PROTECTION AGAINST REVERSE FLOW.  ALLOWS FREE-FLOW IN ONE DIRECTION.  SEAT DESIGN PROTECTS "O" RING SEAL FROM CONTAIMINATION OR FLOW DAMAGE.  INSTALL IN ANY POSITION.  TEMPERATURE RANGE -20° TO +400°F.  OPENS A 3 TO 5 PSI.  VITON SEAL.  STAINLESS STEEL SPRING.  HANDLES WATER, OIL, AND MANY OTHER FLUIDS.