I needed an odd sized filter (set of 2) for a 12 yr old Carrier Fresh air Ventilator. The originals are foam and washable but they take a long time to dry. I got these to put in while I go through the washing/drying process.They seem to work just fine and since they are only used for a day or two, the pack of six will likely outlive the equipment. If the shipping was better, I would have given a 5 Star rating.