2) Unicel C-7479 Replacement Cartridge Filter 75 Sq Ft Caldera Spa PCD75 FC-3085 Industry's most complete line of replacement filter elements Caldera Spas (033017) (Note: C 7375 can also be used as a replacement) ...AND MORE Sharp pleat folds maximize spacing between pleats Tough urethane end caps assure durability for the life of the cartridge