OnliPure Edition Replacement filter 2-year bundle for Zero Installation Purifier Countertop Reverse Osmosis System: FIRST STAGE FILTRATION: 2 pieces 5-micron Prefilter removes Sediment, Rust, and other large particles. Replace every 12 months or as needed. SECOND STAGE FILTRATION: 2 pieces 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. Replace every 12 months or as needed. THIRD STAGE PURIFICATION: 1 piece 75 Gallon Per Day Reverse Osmosis Membrane. This element needs to be replaced only every 2 - 4 years, or as needed. FOURTH STAGE OnliPure ION EXCHANGE POST FILTER: 2 pieces 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. Replace every 12 months or as needed. 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. To reset the reverse osmosis membrane replacement indicator (Solid Red Light) unplug the power supply from the back of the unit and plug it back in while pressing and holding the "push" button. Reverse Osmosis Membrane replacement step-by-step video instructions: