Product review (5 stars): Happy to have found these!
I have three Honeywell HCM-350 humidifiers. When I first owned them Honeywell filters were blue on the outside and they worked well. Honeywell  changed the HAC-504 filter and claimed it was better. Not true at all. I was seriously considering buying all new humidifiers because I couldn't find a good replacement filter. I have tried multiple replacement filters and they have all disappointed me until I found this filter. They are thick enough to hold water, sturdy enough to stand up and they last longer than other brands.

 I highly recommend these filters to anyone needing a replacement filter that actually works.