I have an Aprilaire filter enclosure attached to my furnace which takes a #413 filter. I believe it's designed to give 95% filtration.
It does a decent job but in this ancient house with two cats I'd like to go all the way to a HEPA filter.
I have not been able to find a HEPA replacement so unless anyone has a suggestion , looks like I will have to replace the entire enclosure.
Since I'm not a sheet metal expert, will have to contract this out.