Product review (4 stars): Perfect replacement for the traditional paper filters
I use this filter in my Honeywell HCM350W Cool Mist Humidifier (<a data-hook="product-link-linked" class="a-link-normal" href="/Honeywell-HCM350W-Germ-Free-Cool-Mist-Humidifier-White/dp/B002QAYJPO/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Honeywell HCM350W Germ Free Cool Mist Humidifier, White</a>) and so far after night one it works well.

I've owned this particular humidifier for just over a month now and I've also kept a hygrometer (<a data-hook="product-link-linked" class="a-link-normal" href="/Sainlogic-Hygrometer-Digital-Thermometer-Humidity-Monitor-Indoor-with-Temperature-Humidity-Gauge/dp/B074W89DDV/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Sainlogic Hygrometer Digital,Thermometer Humidity Monitor Indoor with Temperature Humidity Gauge</a>) next to the bed to get a rough estimate of it's effectiveness in the room.

As I said, it's only been one night and I ran the same routine as with the paper filter and by my measure the output was the same with this filter.

I was initially put off by the mention on the cleaning bag of using "muriatic acid" but after reading Q&A and other reviews on this product I've discovered that most are content with using distilled vinegar as an alternative.  So, we'll see how that works out when it comes to cleaning time.

Again, this review might be premature and I will update if anything changes but for the most part I wanted to mention that the overall humidity output seems to be in-line with the paper filter that came with the humidifier.

Note: my rating is lacking a star because of the "muriatic acid" cleaning suggestion and the lack of general information on the companies website.  Even the bag has their web page URL on it suggesting more information available but I couldn't find anything which is why I turned to reviews and Q&A (thanks to all you lovely Amazon reviewers out there)