The replacement filter has a rigid cardboard frame with a MERV 8 rating at 2.5 meters per second. 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 pay attention to the air flow arrows and indicators on the filter. This high quality filter is manufactured by Skuttle. For additional savings, we offer this product in a 3-Pack. (See listing at bottom of this page.)