Capable of capturing the most minute particles, ULPA (Ultra Low Penetration Air) Cartridge Filter meets the highest industry standards for air filtration by providing filtration of 0.1 microns @ minimum of 99.999% efficiency. Ideal for working with allergens, mold, pollen, superfine powders, etc. Cloth Pre-Filter Bag provides extra stage of filtration extending the life of the cartridge filter. Fits all Guardair PowerQUAD 55, 30 and 20 Gallon Drum Vacuums and Vacuum Generating Heads.