Allergy Be Gone Holmes HWF-62 Humidifier Filter with Antimicrobial Protection Measures approximately 4" H x 4 1/2" ID x 6 1/2" OD x 1" Thick. ProTec Antimicrobial helps prevent growth of mold, fungus, algae & other bacteria on filter Fits Holmes models HM1100, HM1300, HM1701, HM1761, HM1281, SCM1801,HM1281, HM1297, HM2409, HM1230, HM1245, HM1275, HM1280. HM1285, HM1290, HM1295, HM1450, HM1740 & HM2408 For optimum performance, replace filter at the beginning of each season or every 2 months depending on use 100% fresh air and satisfaction or your money back. Crafted by Allergy Be Gone.