Product review (2 stars): Works well, for a few days
The filters work great when they work at all.  The filter shown in the picture is the old style which worked better than the new style which has a blue wrap around the filter to help prevent mold.

The problem is that after a few days they stop wicking gradually and eventually dry out even when remoistened.

Mold does build up occasionally but honestly they don't last long enough for that to be a serious problem.