Capable of capturing particles invisible to the naked eye, Guardair's Absolute HEPA (High Efficiency Particulate Air) Cartridge Filter meets industry standards for HEPA air filtration - 99.98% 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 cartridge filter. Fits all 55 Gallon and 30 Gallon Guardair Drum Vacuums and Vacuum Generating Heads. Replacement part.