OnliPure Edition Replacement filter set for Zero Installation Purifier Countertop Reverse Osmosis System. FIRST STAGE FILTRATION: 5-micron Prefilter removes Sediment, Rust, and other large particles. SECOND STAGE FILTRATION: Carbon Block Filter removes Chlorine and other Disinfection by-products. NEW Option for Anti-Scale Carbon Prefilter. Use the Anti-Scale bundle option only when experiencing a short reverse osmosis membrane lifespan (under two years). NOTE: A brand new reverse osmosis membrane is also required when switching to the Anti-Scale bundle. FOURTH STAGE: OnliPure ION EXCHANGE POST FILTER. Polishing OnliPure Post Filter reduces any leftover contaminants after the Reverse Osmosis process to zero TDS. Measure and confirm from your home with a simple TDS meter. Note: Third Stage Purification - 75 Gallon Per Day Reverse Osmosis Membrane is NOT included with this bundle. This element needs to be replaced only every 2-4 years or as needed. If the reverse osmosis membrane is getting clogged due to high levels of hardness present in the water, please use the OnliPure Bundle option with an Anti-Scale Carbon prefilter. Note: If converting from AlcaPure Edition to OnliPure Edition by using this filter bundle, then larger attachment clips are required. To reset the filter change indicator(Blinking Red Light), press and hold the “push" button for 5 seconds.