Tork Sta-Rite Posi Flo II Cartridge Filter PTM135 O-ring Replacement Kit TORK Brand Replacement for the Sta-Rite (Posi-Flo II) Cartridge Filter Model PTM135 This kit offers (2 each) same as: 31935-0001 This kit offers (1 each) same as: WC9-3 This kit offers (1 each) same as: U9-359