I was quite disappointed with how much smaller than my 3M filters these were. I can't complain much because the real sizes were clearly stated when I purchased them. I just did not realize that it is NOT standard behavior in the industry to make the filters significantly smaller than rated size, and it created significant problems in my firnace to make them properly seal and do a good filtering job. Next time, I will need to order a 5" filter to fit properly in my unit which was constructed to safely fit a real 4" filter that was a full 16" wide.