I have been buying the 20" X 25" X 1" version for the past 13 years. The slot I insert the filter in is tight and has a lip on the end. The filter frame holds up well to the maneuvering I have to do. I change filters once a month because my wife is a smoker and I have six cats.
Lasts long and cleans the air much better than the cheap fiberglass filters we used to use. We would probably need 4 sets of the cheaper ones to get halfway close to how good these work for 3 months and still not be as good.