Product review (5 stars): I will buy these forever.
I have bought 2 different filters in the past.  These are the best, by far.  The metal exoskeleton serves to keep the filter in its proper shape throughout its long life.  I use these in the Honeywell HCM 350 humidifier and run it 24 hrs a day during the winter/low humidity time.  THESE ARE THE ONES TO BUY.