Replacement Cycle： For a better, we recommend that you replace the mineral cartridge about once a month 3 Layer Filtration systems: The outer layer adsorbs impurities; the ion-exchange resin in the middle layer heavy minerals, such as calcium; and the inner layer traps additional impurities before the water is released Applicable models: suitable for HM512S, HM612S, HM713, HM713S, HM813S, HM717S The demineralization cartridge hard water, the formation of scale and white for a more comfortable humidification These Humidifier Demineralization Cartridges ensuring safe and water and effectively saving you time and money