The filter pack F4-CUA4 includes a 1st stage 5 micron sediment filter that can effectively remove rust sand and solid impurities in the water to protect the delicate UF membrane; last 6 months. The 2nd stage state-of-the-art UF hollow fiber membrane that uses standard home water pressure to push water through a Semi-Permeable membrane. Suspended particles and materials of high molecular weight are unable to pass through the 0.1 micron UF membrane, leaving you with only fresh clean water and dissolved minerals; it lasts 12 months. 1 x 3rd stage KDF media (or kinetic degradation fluxion media) with activated carbon KDF itself is known to remove chlorine rust unpleasant taste and odor hydrogen sulfide iron lead nickel chromium cadmium calcium aluminium mercury arsenic and other compounds. When used with carbon, KDF can extend the carbon filter life up to 8 times. It also adds a dose of zinc ions to the filter water; last 6 months. 1 x 4th stage Post activated carbon filter, adopting fine coconut shell activated carbon with ultra-micron aperture. This carbon filter absorbs residual chlorine organics humus and odor; last 6 months.