A couple days ago we got our semi-annual checkup on our Lennox and the tech said we didn't need to use their loose pleated paper filters anymore because they now carried an Aprilaire filter that fit the box and would seal much better. For cost reasons we installed the Aprilair 11 version. It cost $54. The tech said that the 13 version was as good as their old 16 version and it cost $93. We thought we ought to give the cheaper version a try first because we had a lot of leak-by with our old filters and there was no use getting the tighter filters. Just wondering if these are any good.