WF2 Vicks Humidifier Wick Filter HF Fits Vicks humidifier models V3100&#44; V3500&#44; V3600&#44; V3700&#44; V3800 and V3900. Measures approximately 5 H x 3 1/2 ID x 5 1/2 OD x 1 Thick. Patented rigid support extended life design. For optimum performance&#44; replace filter at the beginning of each season or every 2 months depending