Product review (5 stars): Good replacement for my HCM350 humidifier.
I spent entirely too long looking at the different options for a replacement filter for my HCM350W.  Ultimately I chose this based on reviews, price, because I could get it quickly (Prime), and because I didn't want to buy multiple of something that I wasn't sure I would like.  As it turns out I like it.  It's nice and thick, seems to disperse hydration well, and while it doesn't have the reinforcement material that I've seen in others it holds up just fine.

I've been using it for almost two months now (running the fan overnight only) and typically have to refill the reservoir every third day.  I tend to let it dry out every 7-10 days or so and I have soaked it in vinegar then bleach (in a gallon Ziploc) once because it started to smell musty.  I'll try to remember to update this when it needs replacement.  For now I'm pretty happy with it though, especially since it survived a disinfection soak.