Product review (3 stars): Product doesn't quite fit
Because we have hard water, I have to frequently order filters for my Vicks Model V3100 humidifier.  I ordered this product since it said the filters fit the V3100, but when I placed the filter in it, I found it was somewhat big (placing the top of the humidifier filled with water did push it down to fit in).  The filter itself was of good quality (hence my 3 star recommendation) but a bit pricey, and I don't think my humidifier works as effectively with this filter as others.  The package even has a picture of my humidifier on it, along with pictures of the Vicks 3500N, Vicks V3900 Series, Vicks 3700, Sunbeam 1118 Series and Honeywell HCM-350 Series humidifiers (a list of other models the filter can be used with is also on the package).  Maybe it works better with those models but I would not recommend it for the V3100.