AAF Flanders 20 in. W x 25 in. H x 4 in. D Pleated 8 MERV Pleated Air Filter (Pack of 6)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