Two of the 6 filters were not properly glued would not be filtering anything. the higher quality filters I bought last year were made night and day better.
I am really happy that I found out to put one on my box fan. I live in the country with dirt and pollen. I use a very good air cleaner, but in the summer I use a box fan to help air flow with my AC. . I could not believe how dirty the filter was after only a few days. This is something I will continue from now on.