Unicel 7CH-552 Replacement Filter Cartridge for 52 Square Foot Top Load, Dimension One Spas Diameter: 7-inch; length: 10 1/2-inch Top end cap: semi-circular handle, 0-inch inner diameter; bottom end cap: 2-inch male thread/mpt, 0-inch inner diameter Pleat count: 216; filter media: 3-ounce reemay 2033; filter area: 52 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications