Bissell Standard Bag & Filter, 3 pk, 3086 Includes 3 bags and 1 secondary filter. Works with 3550 series. Allergen Filtration - captures 100% of pollens, ragweed and dust mites MicroFiltration - over 99% filtration down to 5.0 microns When do I replace my Bag? For best cleaning performance, it is suggested to change your bag when it is 1/2 to 2/3 full. When accumulated, small dust particles can keep the air from circulating, which can reduce the suction in your vacuum When do I replace the filter? Having clean filters is critical to maintain cleaning performance. Over time, filters can become dirty and eventually clog. A dirty or worn filter can diminish the cleaning performance of your vacuum.