Alkaline post-filter replacement for Zero Installation Purifier Countertop Reverse Osmosis System. Note: This filter is also included with the annual filter change bundle. Size: 2 x 10 Fourth Stage Filtration - Must have post filter for any Reverse Osmosis Filtration System. Returns beneficial minerals to water- Calcium and Magnesium. Increases Ph to an alkaline level. No more worries about the Corrosive effects of RO Water. It contains 40% Carbon to remove any remaining impurities. Quick connect fittings built-in for effortless installation. Note: If converting from OnliPure Edition to AlcaPure Edition by using this post-filter, then smaller attachment clips are required.