Pleatco PH3-4-PAIR Replacement Cartridge for Comfort Line/Duroc Top Load, 1 Cartridge Replacement cartridge for comfort line and duroc top load 50 Percent open ABS free flow cores maximize water flow through reemay filter media Antimicrobial end caps resist chlorine degradation and provide support to filter material for a longer life span Replaces unicel and filbur FC-3111; made in usa; microban inhibits the growth of stain and odor causing microbes like bacteria and algea Measures 2-3/4-inches in diameter by 4-15/16-inches in length and 1-1/16-inches of top and bottom hole diameters