Pleatco PSD125U Replacement Cartridge for Sundance Horizontal Spa Cartridge, 1 Cartridge Replacement filter for pool and spa cleaning systems 50% 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 17-3/4-by-2-1/2-inches with closed top Made in the USA