Hoover Y and Z-Micro Filtration Bag, 12 Bags Treated with Ultra-Fresh for Models 4010100Y, 902481001, AH10165, 902419001, AH10040, 4010100Z and 4010075Z Ultra-Fresh treated bags are guaranteed from defects Micro Filtration vacuum bags also capture 99% of particles 5 microns in size, including household fibers and other microscopic allergens The Ultra-Fresh finish on these bags protect against odor and stain-causing microbial growth; This helps keep your bag cleaner and fresher