Particulate Filter - Cabin filter 27277-CL025 (which contains a layer of activated charcoal) can be used in place of cabin filter 999M1-VP051. The activated charcoal provides additional filtration against objectionable outside odors and pollutants such as hydrocarbons, sulfur dioxide, nitrogen dioxide, and ozone. - for Models w/ OE air cond. Cabin filter 27277-CL025 (which contains a layer of activated charcoal) can be used in place of cabin filter 999M1-VP051. The activated charcoal provides additional filtration against objectionable outside odors and pollutants such as hydrocarbons, sulfur dioxide, nitrogen dioxide, and ozone. - The original cabin filter contains a layer of activated charcoal to reduce objectionable outside odors and pollutants such as hydrocarbons, sulfur dioxide, nitrogen dioxide, and ozone. As an economy alternative, cabin filter #999M1-VP051 can be used in its place. 999M1-VP051 does not contain activated charcoal and filters particulates only. -