Product review (3 stars): Decent but short-lived
While it is hard to be passionate one way or the other on a filter, I do have some comments.  The filter itself primarily serves as media to wick water from the basin to the "tunnel" below the fan on my Honeywell humidifier.  You can tell when the filter is starting to harden and absorb less water by how frequently you have to fill the humidifier tank.  It seems to do a good job preventing biological growth and preventing much odor associated with the humidifier, but I am not thrilled with how long they last.  Plan on changing your filter every 30-45 days which can get expensive in comparison to what you pay the humidifiers it is built for.