Pentair R172212 Cartridge Housing Replacement Dynamic Series I Inline Pool and Spa Cartridge Filter Cartridge housing replacement Fits Pentair Dynamic series I inline pool and spa cartridge filter models RDC-25, RDC-25S, RDC-50, RDC-50S Measures 13-27/73-inch length by 13-27/73-inch height by 5-21/25-inch width