Designed to perfectly match All Blueair 500/600 Series SmokeStop 500, 600 Air Purifiers 501, 503, 550E, 601, 603, 650E. Installation is a breeze simply snap them in place and enjoy the ease of breathing cleaner air. A perfect match for your air purifier filter needs. Elevate your home's air quality with LifeSupplyUSA's True HEPA Filter Replacement where health, compatibility, value, durability, and eco-friendliness meet.