AQUAPHOR K3 filter: Replacement filter for primary purification of drinking water. Reduces all common impurities including chlorine, lead, bacteria and solid particles sized down to 5 microns AQUAPHOR K2 filter: Replacement filter for primary purification of drinking water. Reduces all common impurities including chlorine, lead, bacteria and solid particles sized down to 3 microns. AQUAPHOR K7 filter: Replacement filter for final stage of drinking water purification. Removes all common impurities including chlorine, lead, bacteria and solid particles sized down to 0.8 microns. REPLACEMENT CYCLE: AQUAPHOR recommend installing new filters every 12 months – however, if the taste of water output changes, please replace within this timeframe. EASY FIT: Push the button on the appliance, twist out the old cartridge and twist on the new cartridge until you hear a "click" RECYCLE: All AQUAPHOR filters can be recycled - simply visit our website for instructions