Made of HEPA filter paper, the purification efficiency up to 99%, so that the release of healthier air Easy to remove and replace as part of routine maintenance. The filters maintain the cleaning performance of the DYSON DC19 DC20 DC21 while reducing the infiltration of dust, pollen and other allergens into the air you breathe. To keep your vacuum cleaner operating at peak performance, please replace your filter every 2 to 3 months. Package includes 2 HEPA filters for Dyson DC19 DC20 DC21 Washable pre-motor filter; 2 pre-filters for Dyson DC19 DC20 DC21