Hammond Manufacturing's PFF40000 replacement filter is engineered for use with PF/PFA 4XXXX series filter fans. Its unique, patent-pending fluted design significantly increases the time between maintenance cycles, allowing for greater CFM even in challenging environments with particulate matter. The filters are sold in packs of five, providing a convenient and cost-effective solution for maintaining optimal fan performance. For smaller synthetic mesh filters, explore the XPFA and DNFF series.