LifeSupplyUSA Replacement Air Filter for Bionaire 911D Replacement 911D filter for Bionaire Compatible with Bionaire W7, Bionaire 911D, Bionaire C22, Bionaire W6, Bionaire W6S, Bionaire W9, Bionaire W9S, Bionaire W0310, Bionaire C33, Bionaire W2, Bionaire W2S, Bionaire W9H, Bionaire W25, Bionaire W0210, Bionaire W0210S, Bionaire W0305, Bionaire W0340, Bionaire W3040, Bionaire WC0840, Bionaire 2845 900, Holmes W6 Essential for Allergy Sufferers or anyone with Asthma Change air filter at least once per season or more often depending on air quality and use By LifeSupplyUSA