These cartridges are filled with ion exchange resin (cationite in a sodium form) with a high exchange capacity of calcium and magnesium ions. As a result, Ca2+ Mg2+ ions are replaced with sodium ions from the resin and water becomes softened. This way, you can solve the problem of sludge and unpleasant stains on valves, fittings and especially the boiler. The cartridge reduces the problem of hard water for your system and will extend the service internals of your boiler. Having passed through the cartridge, water is deprived of all calcium and magnesium ions. The cartridge come with a male ¼” stem for John Guest quick connectors. Make sure to get the ¼” to 8mm reducers for use in WaterStillar Wall. Also a perfect and easy solution for espressomachines, steam ovens etc. The capacity depends on consumption and your water hardness. Replace at least every 6 months.