Hoover A-Micro Filtration Bag, 12 Bags Treated with Ultra-Fresh for Models 4010100A, 4010001A and AH10135 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