3M Dust Extractor Filter, 33647, is a two pack of polyester replacement filters for the 3M Clean Sanding System's 30-liter and 45-liter dust extractors. The filters help protect the motor unit of the extractor and filter the unit's exhaust air. 3M Dust Extractor Filter, 33647, helps to prevent dust captured by the 3M Clean Sanding System from escaping back into the work area or collecting in the dust extractor's motor. The 3M Clean Sanding System's 30-liter and 45-liter dust extractors feature a continuous filter cleaning system that helps to extend the life of 3M Dust Extractor Filters, 33647. The panel-style filters feature accordion-folded polyester filter material that helps maximize filter surface area. 3M Dust Extractor Filters, 33647, are intended as a secondary filter and should always be used in conjunction with a properly installed 3M Dust Extractor Filter Bag, 33648.