Get cleaner air in your home thanks to these electrostatic Cut-to-Fit furnace filters by 3M. Each fiberglass filter measures 20 inches x 25 inches, but they can be trimmed to fit any furnace. What's more, these reusable filters are washable, which makes them a great choice for people who are environmentally conscious. For best results, vacuum your filter, rinse it, and let it air dry before reusing. These high-quality filters are designed to last up to an impressive months and are made of 100% synthetic polyester.