This round wicking filter from Protec is a replacement humidifier filter. It can be used with a variety of Vicks Cool Mist models, including V3100, V3500, V3600 and V3900. Reinforced for maximum efficiency and longer filter life, it removes minerals and pollutants from the water. Antimicrobially treated, this filter helps prevent the growth of mold, algae and bacteria. This set includes two boxes, each containing two filters.