Traps Water Impurities & Dissolved Solids Before They Become AirborneFor performance, replace filter at the beginning of each season or every 2 months depending on use provide high quality aftermarket replacement parts wick filters which help remove the impurities found in general tap water. These impurities cause the filter to change color as they get trapped in the wick. as more and more minerals become trapped more of the filter will change color. eventually the filter will no longer be operating the humidifier effectively, which means it is time to change the filterFits Models: HM1888, HM1889, HM2059, HM3000, HM3800, HM3850, HM4000, HM1855, HM1865, HM1850, HM1851, HM1845, HM1840, HM1895, HM2060WFits Models: SCM1866, SCM1895, SCM1896[Product name] humidifier filter[Main function] humidificationcolour:black & whiteMaterial:Composite materialmodel:HWF75Package Contents:2 x FiltersOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.