UpStart Battery 2-Pack Replacement Blueair 205C Air Purifier Filter - Compatible Blueair 200 & 300 Air Filter Replacement Blueair 205C Humidifier Filter; Quantity: 2 Replaces Blueair 200 & 300 Air Filter Gradient filter design maximizes airflow while removing harmful particles to 0.1 microns in size For best results, change air filter at least once per season or more often depending on air quality and use. Essential for Allergy Sufferers. On Sale for a Limited Time!