This is the high efficiency filtering media, which is the heart of your air cleaner. To maintain optimum efficiency, the filter should be inspected quarterly and replaced at least every 12 months. The filter may require more frequent replacement if the filter appears dirty to the point of blocking air flow through the heating/cooling equipment. When replacing the filter be sure to keep the pleat spacers as they can be used for the life of the mechanical air cleaner. This high quality filter is manufactured by Carrier/Bryant. For additional savings, we offer this product in a 3-Pack. (See listing at bottom of this page.)