The ZL Series air filters feature extended-surface pleated-media. The media utilized is made of 100% synthetic fibers and is pleated in a tapered radial configuration. A heavy duty, recycled expanded metal reinforcement is laminated to the air-exit side of the media by a thermo-setting adhesive to maintain continuity of the radial pleats. The expanded metal is galvanized to resist rust and corrosion. The pleated cartridge is bonded to the peripheral interior of the outer frame and a heavy-duty moisture-resistant beverage board incorporating post-consumer material is utilized for an encasing frame. The frame face is internally laminated to the pleated cartridge apexes.