Replacement Cartridge for Dimension One 75, @Home Hot Tubs (Open with Twist Lock), 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 10-5/8-inches with castle top and special-lock-bottom Made in the USA