Bosch Activated Charcoal Workshop Cabin Air Filters feature a multi-layer media that offers a 99 percent efficiency rate at 3 microns or greater in keeping dirt and other particles from entering vehicle heating and air vents 1st Layer - Non-woven pre-filter layer captures larger particles 2nd Layer - Electrostatically charged microfiber layer attracts and holds elusive smaller particles 3rd & 4th Layers - Non-woven cover layers add stability to protect the microfiber layer from damage and act as an additional barrier to harmful elements 5th Layer - Activated charcoal layer absorbs toxic and foul-smelling gases such as ozone, nitrogen oxide, sulfur dioxide and hydrocarbons which results in fresher smelling air and reduced windshield hazing Compatible with select vehicles (Note: vehicle trim level may affect fitment - verify specific vehicle fitment details with fit checker above): BMW: 2001-05 320i, 2000 323Ci, 1999-00 323i, 2001-06 325Ci, 2001-05 325i, 2001-05 325xi, 2000 328Ci Compatible with (continued): BMW: 1999-00 328i, 2001-06 330Ci, 2001-05 330i, 2001-05 330xi, 2001-06 M3, 2004-10 X3, 2002 Z3