Unicel C-2613 Replacement Filter Cartridge for 12 Square Foot Rainbow 29 Diameter: 2 7/8-inch; length: 29 1/4-inch Top end cap: open, 1-1/16-inch inner diameter; bottom end cap: open, 1-1/16-inch inner diameter Pleat count: 41; filter media: 4-ounce reemay 2040; filter area: 12 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications