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: 2011 1 Series M, 2008-13 128i, 2008-13 135i, 2013 135is, 2006-11 323i, 2006 325i, 2006 325xi Compatible with (continued): BMW: 2007-13 328i, 2009-13 328i xDrive, 2007-08 328xi, 2006 330Ci, 2006 330i, 2006 330xi, 2009-11 335d, 2007-14 335i, 2009-13 335i xDrive, 2013 335is, 2007-08 335xi, 2013-15 X1