Compatible with Blueair Pro M, Pro L and Pro XL Air Purifiers. Filter Requirements: Pro M = 1 Filter, Pro L = 2 Filters, Pro XL = 3 Filters Features a V-shape butterfly fold, and is designed for maximum removal of airborne pollutants such as pollen, dust, pet dander. To maintain optimal performance, filter change is recommended every 6-12 months (depending on air quality and use). Brand New, by LifeSupplyUSA.