1. COMPATIBLE MODELS - Our humidifier filters are compatible with honeywell HAC-504, HAC-504AW, HAC-504V1, HCM-350, HCM350,HCM350W, HCM-350B, HCM350B, HCM-350W, HCM-350B-CST, HCM-300, HCM-300T, HCM300T, HCM-305T, HCM310T, HCM-315T, HCM305BCST, HCM-450B-CST, HCM450BCST, HCM-500, HCM-530, HCM530, HCM-535, HCM353, HCM-535-20, HCM53520, HCM-540, HCM550, HCM-550-19, HCM55019, HCM-551, HCM-560, HCM560, HCM-600, HCM-630, HCM630, HCM-631, HCM631 humidifiers. 2. STANDARD WHITE HUMIDIFIER FILTERS - Our humidifier filter replacement for HAC-504 is made of high-quality rigid reinforced mesh paper and adopts hot glue strips and dense construction to improve filters structure once wet and reduce sagging. humidifier filter with higher efficiency, lower pressure, the quality, and the largest surface area ensures expelling moisture back into the air as you expect 3. EXCELLENT PERFORMENCE - Enjoy moist air in winter with humidifier filter replacement for humidifier to ease uncomfortable symptoms caused by dry air. The absorbent mesh paper works with the humidifier to filter impurities in the water, preventing white powder from entering the indoor air and depositing on anything within sight, and keep your humidifier maintaining its peak performance 4. COST-EFFECTIVE GOODS - Package includes 4 x Standard White Humidifier Filter Replacement for Honeywell HAC-504. Filter Dimensions: H: 7.0 x L 5.3 x W: 4.8 inches. Warm Tips: For results, please fill the humidifier tank with distilled water. Excessive use of hard water will degrade filters and cause them to turn yellow prematurely.