The FAMCO FRB Furnace Filter Rack/Base has removable channels to accommodate filters from 1 to 4 inch in updraft and downdraft installations. Easy filter access with use of snap clips and simplified “door”. Quality constructed in heavy 22 gauge Galvanized steel for durability and longevity. The FAMCO FRB Furnace Filter Rack/Base come in a range of sizes to fit common sized ducting: 14 inch x 20/25 inch, 16 inch x 20/25 inch, 18 inch x 20/25 inch, and 20 inch x 20/25 inch. The FAMCO FRB Furnace Filter Rack/Base is manufactured by FAMCO in the United States and comes with a 1-year warranty against product defects and workmanship. If you have any questions about this product, please refer to the FAQs above or feel free to contact us by phone or email.