UpStart Battery Replacement Honeywell HCM-350B Humidifier Filter - Compatible Honeywell WF2 Air Filter Replacement Honeywell HCM-350B Humidifier Filter Replaces Honeywell WF2 Air Filter Traps Water Impurities & Dissolved Solids Before They Become Airborne For best results, change air filter at least once per season or more often depending on air quality and use. Essential for Allergy Sufferers. On Sale for a Limited Time!