Too often overlooked, your cabin filter is there to reduce dirt, dust, hair, odors, and other contaminants from entering the cabin (and ultimately, your lungs). By replacing the cabin filter you will not only be breathing cleaner air, but your heating and air conditioning systems will be work more efficiently and last longer. The cabin filter is part of the regular scheduled maintenance of your car and should be replaced at the first indication of contamination. Manufactured by key filtration supplier to BMW, MANN.