Product review (2 stars): I have been using other filter sizes from Filters-Now and ...
I have been using other filter sizes from Filters-Now and they all fitted perfectly in other humidifiers I have. This one was the first WF2 I bought from Filters-Now and it is much shorter in diameter (close to 2 inches shorter) then the original Kaz WF2 filter, the height is ok.

I needed to soak the filter and then carefully strecht it so it would fit in the humidifier.  I don't know how efficient it will work and how long it will last. Next time I will look for another filter brand.