Product review (5 stars): Easily modified to work with my super old fan
My house is older (1955) and has an exhaust fan through the kitchen wall to the outside.  There was no filter, so I decided to try adding this one to hopefully keep the fan clean and working well.  It is the right diameter, however my fan has a pull chain and I couldn't find a filter made with a notch for that.  So I just cut a small hole in the filter for the chain and it's working just fine.