Product review (5 stars): Good Price and Better Product than the Original Filter
I liked the humidifier, but the filter that came with it did not cover the opening well.  A lot of it would remain dry and I doubted the effectiveness of the system.  I almost discarded the humidifier until I thought to look on Amazon for replacement filters.  I found these and the idea of having something in the middle of the filter to hold it upright made sense.  I bought it and these things are great.  They prevent the wet filter from sagging and that way the entire opening is blocked by the filter insuring better moisture transfer.