The Fleece Filter Bag works with 9 gal dust extractors to effectively capture dust and debris. These bags can help users move toward OSHA silica regulation compliance and increase their productivity. This filter bag acts as a preliminary filter, capturing most of the debris and dust to increase the life of the main filter. The port cover securely closes opening of the filter bag and keeps the dust and debris inside during the disposal process. It's for dry use only and will be damaged by wet-vacuuming.