Our most popular filter, the Standard Cartridge Filter (6-Pack) is ideal for most industrial and commercial cleaning applications. Operates at a minimum of 98% efficiency for particles up to 10 microns. For finer filtration capability, substitute Guardair's HEPA or ULPA filters. Fits all 55 Gallon and 30 Gallon Guardair Drum Vacuums and Vacuum Generating Heads. Replacement part.