Feature: 1. [For Blueair 500 600 Series] This filter is specially designed for Blueair classic 500 600 series air purifiers, can be used for Blueair classic 501, 503, 510, 550e, 555eb, 601, and more. 2. [Excellent Performance] The filter has excellent filtration performance, which the micro and macro pores can remove 99.97% of the dust in the air as small as 0.3 microns. 3. [Practical and Powerful] The air filter works efficient and powerful, which is a perfect choice for those sensitive to the surrounding air. 4. [Safe Ensuring] And the filter will not release harmful substances, good for your health, you can use with confidence. 5. [3 Pcs Set] For best performance, it is recommended to replace every 3 to 6 months, this set includes 3 pcs filter for you, enough for about one year. Specification: Item Type: Air Purifier Filter Material: High efficiency particulate air filter, cotton. Package List: 3 x Air Purifier Filter Note: 1. For best performance, it is recommended to replace the filter every 3 to 6 months. Easy to replace and disposable use, no tools required.2. To ensure a happy purchase, please check the part number and size of filter carefully.