Capable of capturing particles invisible to the naked eye, the Absolute HEPA (High Efficiency Particulate Air) Cartridge Filter meets industry standards for HEPA air filtration – 99.97 percent efficiency for particles up to 0.3 microns. Ideal for working with allergens, powders, and superfine particles. Cloth pre-filter bag provides extra stage of filtration extending the life of the filter. Fits 15 Gallon Nortech vacuums.