Unicel C-7440 Replacement Filter Cartridge for 40 Square Foot Purex CF-40 Diameter: 7-inch; length: 11 1/8-inch Top end cap: open, 2 15/16-inch inner diameter; bottom end cap: open, 2 15/16-inch inner diameter Pleat count: 155; filter media: 4-ounce reemay 2040; filter area: 40 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications