Unicel C-4405 Replacement Filter Cartridge for Rainbow DSF-50, Waterway Plastics Diameter: 4 15/16-inch; length: 6 5/8-inch Top end cap: open, 2-1/8-inch inner diameter; bottom end cap: open, 2-1/8-inch inner diameter Pleat count: 158; filter media: 4-ounce reemay 2040; filter area: 50 square feet Get more efficient filtration and better water clarity with Unicel filters Longer time between cleanings; meets oem specifications