Pleatco PDM25P4-M Replacement Cartridge for Dream Maker Spas (MICROBAN), 1 Cartridge Replacement cartridge for dream maker spas 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 4CH-21 and filbur FC-0136; made in usa; microban inhibits the growth of stain and odor causing microbes like bacteria and algea Measures 4-3/4-inches in diameter by 8 1/8-inches in length and 1-1/2-inches off bottom hole diameter