Unicel C-7491 Replacement Filter Cartridge for 75 Square Foot Pac-fab Seahorse-300 Diameter: 7-inch; length: 18 7/16-inch Top end cap: open, 2 5/8-inch inner diameter; bottom end cap: open, 2 5/8-inch inner diameter Pleat count: 150; filter media: 4-ounce reemay 2040; filter area: 75 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications