Round wicking filter for use in some Vicks and Kaz humidifiers, 24 pack.  For use with:  Vicks Natural Mist Models V3100, V3500, V3600 and Kaz HealthMist Model 3020.

For the V3100 you will "flatten" the filter out.  If you examine your original filter you will see that it, too, is a round filter.