Pleatco PFAB125-4 Cartridge/Grid Replacement for Pentair/Pac Fab Seahorse 500 with Stainless Steel Tank and Sea Horse Fsh-500 Fiberglass Tank Pleatco Cartridge Filter replacement Cartridge/Grid Pentair/Pac Fab Seahorse 500 (Stainless Steel Tank), Sea Horse FSH-500 (Fiberglass Tank), (4 required) Unicel: C-7493; FILBUR: FC-2194; Mfg.No.:1722849, 172887, R173318