Flanders' Pre-Pleat® 40 LPD achieves the highest dust holding capacity and the lowest pressure drop in the industry. These filters are UL 900 classified. 100% synthetic non-woven, proprietary media that can be recycled. Newly designed expanded metal is continuosly laminated on the air leaving side to provide pleat stability while eliminating flutter during operation. Heavy-duty, two piece, moisture-resistant frame includes diagonal and horizontal support members bonded to the media on the air entering and exiting sides for unsurpassed frame strength. Interlocking corners and positive media-to-frame seal reduce the possibility of air-bypass.