Self cleaning filter bag for use with CTL MIDI (suits superseded CT MINI & MIDI models - not suitable for new CT MIDI-2 575839), allows for optimum usage of filter bag volume and constant suction power. Caking of dust reduces effective suction power dramatically resulting in poor extraction efficiency and performance. The self cleaning Festool filter bag prevents caking with its unique pliable fleece material.  This means that your Festool dust extractor continues to deliver full suction until the bag is completely full. The filter bag traps dust particles down to 5 microns, reducing wear and tear as well as the expense of frequent filter replacement. The tear resistant material and integrated closure on the bag shuts the opening to prevent spilling.