Unicel C-8474 Replacement Filter Cartridge for 75 Square Foot Astral 2507 Ce Terra Diameter: 8 15/16-inch; length: 15-inch Top end cap: open, 3-3/4-inch inner diameter; bottom end cap: open, 3-3/4-inch inner diameter Pleat count: 165; filter media: 4-ounce reemay 2040; filter area: 75 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications