Unicel C-4351 Replacement Filter Cartridge for 50 Square Foot Icon Spas Diameter: 4 1/4-inch; length: 23 3/4-inch Top end cap: semi-circular handle, 0-inch inner diameter; bottom end cap: open with molded o-ring, 2 5/16-inch inner diameter Pleat count: 202; filter media: 3-ounce reemay 2033; filter area: 50 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications