Unicel C-5346 Replacement Filter Cartridge for 50 Square Foot Marquis Spas, Old Style Diameter: 5 3/16-inch; length: 14 1/8-inch Top end cap: closed, 0-inch inner diameter; bottom end cap: open, 1 5/8-inch inner diameter Pleat count: 180; 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