Flanders Economy Pre Pleat 40 extended surface pleated filters are designed to operate in most every type of installation. These filters have an average atmospheric dust spot efficiency range of 25-30% per ASHRAE Standard 52.1 test methods. Pre Pleat 40 filters offer greater efficiency and service life than disposable filters, pad and frame systems, or metal washable filters. The overall design of this product makes these filters the accepted choice in applications requiring high performance and extended service.