Product contains a four pack of premium 2022 upgraded for Blue Honeywell Blue Humidifier Filters for Filter A, HAC-504, HAC-504AW, and HAC504V1. The best wicking filters for Honeywell humidifiers.We manufacture our filters by utilizing a special interweaving locking pattern in order to keep the filter rigid and upright, even when soaking wet. Our competitors don't do this and use cheaper manufacturing methods that leads to worse performance.Designed to fit the following for Honeywell Humidifier Models HCM350W, HCM-350, HCM350, HCM-350B, HCM350B, HCM-350W, HCM-350B-CST, HCM-300, HCM300, HCM-300T, HCM300T, HCM-305T, HCM305T, HCM-310T, HCM310T, HCM-315T, HCM315T, HCM305BCST, HCM-450B-CST, HCM450BCST, HCM-500, HCM500, HCM-530, HCM530, HCM-535, HCM353, HCM-535-20, HCM53520, HCM-540, HCM540, HCM-550, HCM550, HCM-550-19, HCM55019, HCM-551, HCM551, HCM-560, HCM560, HCM-600, HCM600, HCM-630, HCM630, HCM-631, HCM631Our filters are treated to increase filter length but the exact time to replace the filter will vary based on your water and air quality. To increase filter length use cold distilled water, flip daily, and soak in white vinegar. If you have hard water, the filter be stained yellow.Colour As shownMaterial wood pulp paperPackage Contents 4 * filtersOnly the above package content, other products are not included.Note Light shooting 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.