Product review (5 stars): Buy these
Working well. If you don't let them dry out every day (if you use humidifier only at night), they will get moldy. I bought these to replace a moldy original manufacturer filter, so I'm not really clear on whether the manufacturer filter resists mold better or not (sorry).  They help get a lot of moisture into the air (comparable to original filter).  Finally found an article on consumer reports that says to take your humidifier apart every day and rinse it then let it air dry. Weekly you should actually de-scale/disinfect.  I've been drying everything daily and nothing is moldy now, but until I started doing that it kept getting moldy all the time.