They are too small. The 3M filters I have used in the past fit snuggly and didn't have gaps at the top and sides to allow unfiltered airflow. Wish I had only bought one. Cheap way to make these.
I have been using these filters for many years. They are a little morecostly but the job they do is well worth it. I have lung issues andasthma. These filers are the best for that.
This is a well designed filter and does a great job of filtering without producing excessive resistance to flow and therefor does not strain the fan motor.