Product review (5 stars): Works better than original pad
I have a aprilaire 500 humidifier that uses this size pad and due to size restriction of area of furnace had to use 1 size smaller humidifier than I wanted (right on edge to use bigger) I bought this pad locally first and it is more efficient at raising to humidity in the house than the metal OE one. Only issue is will have to be replaced more often since it uses a fiber type pad which if you try to clean will fall apart but is small price to pay for better efficiency of unit.