Hepa filter – captures 99. 97% of particles larger than 0. 3 microns Works with high-cfm dust extractor – designed for use with Bosch gas20-17a 300-cfm dust extractor Low-stick surface – Improves the filter-cleaning process Filtering bag Recommended – use with a filter bag is recommended when this HEPA filter is used, to maximize air flow and to protect the filter from being directly exposed to abrasive materials and sharp objects Bosch PRO+GUARD – provides HEPA filtration as part of an end-to-end dust-protection system