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.Item Type:AirPurifierFilterMaterial: Highefficiencyparticulateairfilter, cotton.wang-edit-text{font-family:'Arial'important;}.wang-edit-text table {border-top: 1px solid000;border-left: 1px solid000;}.wang-edit-text table td,.wang-edit-text table th {border-bottom: 1px solid000;border-right: 1px solid000;padding: 3px 5px;}.wang-edit-text table th {text-align: center;}Package List3 xAirPurifierFilterNote1. 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.