Catalog Plastic Check Valves 3300 Series Category: Inline Check Valve, Plastic Check Valve Design: Economical, Zero Leakage, Compact Configurations: Barb Materials: Nylon, Polypropylene, Kynar O-rings: Viton, EPDM, Silicone Max Pressure: 125 psi Crack Pressure: 1/2 psi