Medium Efficiency Pocket Filters Summary As a secondary filter, the Bag Filter adopts double U shape metal framework, its filtering bag is locked to the supporting matrix bars within the U shape framework and tightly pressed by both adjacent matrix bars and the supporting matrix bars, resulting in a strong structure. Features * It filter class is subject to 40-45% ( F5) , 60-65% ( F6) , 80-85% ( F7) , 90-95% ( F8) ( EN779) . * It filtering material is a synthetic fibre of high quality.