The Aqua-Pure™ AP5527 is the replacement cartridge set for the discontinued APRO5500 reverse osmosis system. This is a unique cartridge being both a pre and post type cartridge, which ships as a 2-pack. It performs filtration before and after the main filter for removing the more challenging, finer sediments from drinking water. Product Benefits: Reduction of: Sediment/Rust, Chlorine taste and smell, Lead, Arsenic, TDS, Turbidity, Parasitic Protozoan Cysts, Radium, Barium, Cadmium, Chromium, Copper, Fluoride & Selenium Sanitary Quick Change (SQC) cartridge design helps provide fast & easy cartridge change-out with minimal effort Advanced multi-stage reverse osmosis water filtration system helps provide cleaner, better tasting drinking water through a dedicated faucet The 3M™ Aqua-Pure™ Under Sink Reverse Osmosis Replacement Water Filter Cartridge AP5527, set for use in the AP-RO5500 reverse osmosis system, installs under the kitchen sink and delivers cleaner, clearer, better tasting drinking water through a dedicated drinking water faucet. This system provides water filtration on demand for drinking water, coffee, tea, baby formula, and cooking purposes. Our universal system design allows for use on both chlorinated (municipal) and non-chlorinated (well water) systems. Replacement System Membrane The Aqua-Pure™ APRO5500RM Reverse Osmosis Membrane has been discontinued. The APRONEL24 is the APRO5500 Reverse Osmosis Alternative.