You should get a look at that coil to see if it has any buildup you need
cleaned. Air Bear is a good positive sealing filter . Dirt buildup on
the coil will cost alot more in the long run than a quality filter, in
lost eficiency, cleaning of coil, house cleaning, and breathing cleaner
air and dirty ducts collecting crap. They may be 400 or so installed
but it is worth it.