Unicel C-8405 Replacement Filter Cartridge for 180 Square Foot Purex DM Diameter: 8 7/8-inch; length: 39-inch Top end cap: open, 4 0/0-inch inner diameter; bottom end cap: open, 4 0/0-inch inner diameter Pleat count: 139; filter media: 4-ounce reemay 2040; filter area: 180 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications