Holmes aftermarket humidifier wick replacement filter with antimicrobial agent. Measures approximately 7 1/2 H x 5 1/4 ID x 7 1/4 OD x 1 Thick. Fits Holmes humidifier models HM5100, HM1800, HM1840, HM1845, HM1850, HM1851, HM1855, HM1865, HM1888, HM1889, HM1895, HM1975, HM2059, HM2060W, HM2090, HM3000, HM3800, HM3850, HM7600, and HM4000. *HM3000 and HM4000 require 2 filters. *HM3800 and HM3850 require 3 filters. Honeycomb filtration to trap mineral pollutants found in water and help prevent them from entering your home. For optimum performance, replace filter at the beginning of each season or every 2 months depending on use.