Replacement cartridge for waterway skim filter 10 * 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 C-4310 and filbur FC-3077; made in usa; microban inhibits the growth of stain and odor causing microbes like bacteria and algea * Measures 4-1/4-inches in diameter by 4-inches in length and 2-1/16-inches of top and bottom hole diameters