After installing a set of ATP activated carbon CAF's in my Mazda 3 (it's a two panel design) I haven't found it to be worth spending any extra money. We're not talking big bucks and ATP is a brand I like, but I still smell diesel exhaust, skunks, and the local landfill just as much as I did before. It's possible that the PPM of these chemicals have been reduced, but my nose can't tell the difference.