To keep your Festool CT 36 Dust Extractor Running in top condition, and adapting to your needs, you need to use the best Accessories like; Festool's newly created SELFCLEAN Filter Bag it is a self-cleaning filter bag that solves a problem that plagues other dust extractors and vacuums. During normal use, fine particles of dust cling to the inner lining of the filter bag resulting in caking. This coating of dust lowers the effective suction power dramatically resulting in poor extraction efficiency and performance. Caking can also cause additional strain on your dust extractor's motor and contribute to premature failure. Festool has addressed this issue by developing a unique pliable fleece filter bag. Because the bag is not rigid like many other types of bags, such as paper bags, it prevents caking. When this occurs, you're paying full price for a partially used bag. The Festool filter bag also serves as a pre-filter and is able to trap dust particles down to five millionths of a meter, or 5 microns. This is about the same size as a red blood cell.