Inside the 10 Stage Filter Cartridge10 Stages of Protection Against Major Water ContaminantsU.S. Patent No. 6197193 B1Stage 1- 100 micron sponge filter. Traps larger solids sediments such as RUST.Stage 2- 8 oz. of KDF-55. KDF-55 is a patented alloy. It removes free Chlorine and some Heavy Metals t