Unicel C-4310 Replacement Filter Cartridge for 10 Square Foot Skim Filter Diameter: 4 1/4-inch; length: 4-inch Top end cap: open, 2-1/16-inch inner diameter; bottom end cap: open, 2-1/16-inch inner diameter Pleat count: 216; filter media: 3-ounce reemay 2033; filter area: 10 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications