Pleatco PSR135-4 Replacement Cartridge for Sta-Rite Posi-Flo T-135TX, Open with 12 Concentric Slots, 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 34-1/2-by-4-3/16-by-4-3-16 Made in the USA