Baleen Filters AK-3031 Pool Filter Replaces Unicel C-4440, Pleatco PSD40-4, Filbur FC-2710-Pool and Spa Filter Cartridges, 40 sq. ft. Media Area 40 sq ft, 4 5/8" OD, Castle Top, Open Hole: 2 1/16" Bottom, 16 3/4" Long, AK-3031 1 Year Warranty - Baleen Filters are made from Durable and Efficient USA Made Reemay Fabric - Washable Fabric Extends Your Filter's Life 40 sq. ft. 4000 Series Cartridge for Sundance, replacement of Unicel C-4440, Pleatco PSD40-4 Baleen Filters Top: Castle Bottom: Open Hole: 2 1/16" Guaranteed Perfect Fit - Extremely Durable - Wash & Reuse - Most Energy Efficient - Withstands High Pressures & Temperatures