Allergen filtration replacement vacuum bag ideal for allergy sufferers. Retains dust pollen bacteria and other contaminants while you vacuum. This system combines a high-filtration paper bag lined with electrostatically charged fibers and a Micro-Fresh filter pad to retain fine dust and pollen particles down to 0.1 micron in size. The air returning to the room is 99.9% fresh based on laboratory tests. Type U fits Swivel Glide and Ultra.