10 Pack Humidifier Filter for Protec WF2 Extended Life Vicks WF2; Fits Vicks V3500N, V3100, V3900 Series, V3700, Sunbeam 1118 Series & Honeywell HCM-350 Series; Fits Protec WF2 Extended Life Vicks WF2; Fits Vicks V3500N, V3100, V3900 Series, V3700, Sunbeam 1118 Series & Honeywell HCM-350 Series; For best results, change air filter at least once per season or more often depending on air quality and use. Traps Water Impurities & Dissolved Solids Before They Become Airborne Brand New Individually Sealed Designed & Engineered by LifeSupplyUSA