Single-effected/double-effected auto air filter:Single-effected (white color): particle filtrationDouble-effected (mixed color of black & white): Particle Filtration & Polluted air filtration Static nonwoven filter core (single-effected) / Activated carbon nonwoven compounded filter core(double-effected) Enhanced polypropylene plastic frameFilter core and plastic frame are fixed by plastic injection molding directly with compact configuration.Single-effected filter can eliminate the inhalable particulate matter from outside such as the pollen/particle/microbe, etc effectively to purify the air inside the automobile.Double-effected filter can eliminate the inhalable particulate matter from outside such as the pollen/particle/microbe, etc, but also can get rid of the smog smell /toluene/sulfur dioxide such harmful gas effectively to purify the air inside the automobile