Unicel C-4324 Replacement Filter Cartridge for 25 Square Foot Pleatco Skim Filter, Spa Manufacturers, Gatsby Spas Diameter: 4 5/8-inch; length: 9 3/4-inch Top end cap: molded cone handle, 0-inch inner diameter; bottom end cap: open, 1 9/10-inch inner diameter Pleat count: 173; filter media: 3-ounce reemay 2033; filter area: 25 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications