Unicel C-7455 Replacement Filter Cartridge for 55 Square Foot Hayward Cx550re, Muskin P/N 58039, FE-127 Diameter: 7-inch; length: 19 5/8-inch Top end cap: open with molded gasket, 3 0/0-inch inner diameter; bottom end cap: open with molded gasket, 3 0/0-inch inner diameter Pleat count: 105; filter media: 4-ounce reemay 2040; filter area: 55 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications