They’re quite easy to make: https://cleanarair.com/
https://www.homedepot.com/p/Nordic-Pure-20-x-20-x-1-Allergen-Pleated-MERV-12-FPR-9-Air-Filter-12-Pack-20x20x1M12-12/312515532 is the best deal on filters I’ve seen.
They’re quite easy to make: https://cleanarair.com/
https://www.homedepot.com/p/Nordic-Pure-20-x-20-x-1-Allergen-Pleated-MERV-12-FPR-9-Air-Filter-12-Pack-20x20x1M12-12/312515532 is the best deal on filters I’ve seen.