Pad and Frame Air Filter (1 Frame and 6 Pads) - 7" x 7" x 3/4" Quantity:Default these can be purchased in

these can be purchased in any conceivable size

In general

the greater it's resistance to airflow

if not you can measure it or check the HVAC unit and the owner‰۪s manual

than standard fiberglass filters purchased at retail outlets

Pad and Frame Air Filter (1 Frame and 6 Pads) - 7" x 7" x 3/4" Quantity:Default these can be purchased inIncludes one Frame and PACK of 6 pads The Pad and Frame Air Filter involves a permanent frame and replaceable filtration pad inserts. The permanent frame is constructed of space age plastics that are resistant to corrosion, oxidation and deterioration. Filtering inserts are anti microbial and are more efficient in capturing particles, such as dust, ragweed, pollen, etc., from the air stream, than standard fiberglass filters purchased at retail