Unicel 2 New C-8326 Pool Replacement Cartridge Filter 125 Sq Ft Sundance Spas Industry's most complete line of replacement filter elements Sundance Spas (6540 488) (Note: Models dated before 2006, contains a core block/plug) ...AND MORE Sharp pleat folds maximize spacing between pleats Tough urethane end caps assure durability for the life of the cartridge