Pleatco PCST80 Replacement Cartridge for Coast Spas 100, Waterway Plastics, 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 21-5/16-by-2-1/8-by-2-1/8-inches Made in the USA