Blue Pure 211+ Yellow Washable Pre-Filter, Removes Pollen, Dust, Pet Dander and Other Airborne Pollutants, Buff Yellow, by Blueair REPLACEMENT PRE-FILTER for Blue Pure 211+ air purifier or for adding a splash of color to your room. REDUCES larger particles in the air; such as dust, lint, pollen and pet dander. SPECIALIZED FABRIC BLEND to be machine wash safe and hanged to dry, PERSONALIZE YOUR PURIFIER with up to 5 different colors; Diva Blue, Buff Yellow, Crystal Pink, Lunar Rock and Dark Shadow RECOMMENDED TO CLEAN once every 2 - 3 months or as needed based on your environment