The filters help maintain the cleaning performance of the Dyson DC19 DC20 DC21 DC29 vacuum cleaner, while reducing the infiltration of dust, pollen and other allergens present in the air you breathe. The Dyson 2-in-1 blue rear-mounted vacuum filter is Made of HEPA, a highly efficient filter paper, it can filter 99% of fine particles in the air, so that the air purified by the vacuum cleaner can be removed to reduce secondary pollution. The Dyson filter is perfect for pet owners. The Eco-Ready, anti-allergy, and Power Filtration features will keep your home clean. For best results, we recommend replacing the filter every 2-3 months for best performance.