Genuine Blueair replacement filter compatible with the Blue Pure 211+ Auto only. This filter is not compatible with the standard 211+ or MAX models. If used with the 211+ or MAX, the clean air delivery rate (CADR) will decline.The Combination Particle + Carbon filter protects against both gaseous and particulate contaminates. Advanced polypropylene filter media removes particle pollutants from your indoor air, such as pollen, dust, and pet dander. At the same time, a layer of activated carbon mesh traps light household odors from pets, cooking, smoke, and more. The 360-degree design allows the filter surface area to be over 20 square feet in size.