These filter are a waste of time and money! These filters are undersized- not 20"x20"x4" which is printed on the side of the filter! They are 19 3/8"x19 3/8"x 3 5/8" Which means they do not seal! Air leaks around them, which means they only filter a small fraction of the air going through the air handler.
The filters are well made and ask described. problem. Was that somewhere just a little bit of size? Making it extremely difficult to fit them in advance that they're made for.
These are the worst filters I have seen.The frames are flimsy.The filter material is thin and bunched at one side.These cannot work effectively.I regret having purchased them.