Pentair 33455-1050 Spring Check Valve Gasket Replacement Sta-Rite Pool/Spa D.E. and Cartridge Filter Spring check valve gasket replacement Fits Pentair Sta-Rite System 2 modular media cartridge filter models PLM100, PLM125, PLM150, PLM175, PLM200, PLM300 Also fits Pentair Sta-Rite System 2 modular pool/spa D.E. filter models PLD50-DE, PLD70-DE