Pleatco PIN28 Replacement Cartridge for Intex 520 "D" Version, Krystal Klear Models 520/530, Sand-n-Sun, Wet Set, Easy Set, 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 12-3/16-by-2-by-2-inches Made in the USA