Filter are most likely fine. They were not packaged well and two of the four have crushed corners. I don't plan on using them for three months since I just used my last Merv 8.
We had a Trane electronic air filter and a Boair electrostatic 1" filter. Replaced both with a Filterbuy MERV 13 20" x 21" X 4" filter. We saw immediate improvement in air quality and dust removal. My wife's noses was always congested and she was light headed. If we were away for a few days, she would feel good until she returned to this house and all her problems would return. . We thought the duct work was leaking and pulling in dust. The other filters were not removing the dust, just recycling it!
there are not near as many pleats in these filters, so I was disappointed in that as I feel they will not last as long or do as good a job as better quality filters would.
When you advertise something as 20x20x4 it should actually be close to that size. Instead you sent me 19x21x3.5. It totally does not fit. I'm sending them back.