MicronAir Particle Cabin Air Filter, fits BMW: M5 1991-2005 requires 1 filter, 7 Series 1991-1995 requires 1 filter, 5 Series 1991-1996 requires 1 filter. Traps Harmful pollutants before they reach your vehicles interior and provides cleaner air for allergy and asthma sufferers. Vehicle manufacturer recommends filter be changed every 6 to 12 months.