MicronAir Particle Cabin Air Filter, fits Ford Windstar 1999-2003 requires 1 filter, Freestar 2004-2007 requires 1 filter, and Mercury Monterey 2004-2007 requires 1 filter. Traps Harmful pollutants before they reach your vehicle's interior and provides cleaner air for allergy and asthma sufferers. Vehicle manufacturer recommends filter be changed every 6 to 12 months.