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. 3 Layer : 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. Package includes: 3Pcs Humidifier Demineralization Cartridge