When I bought #425, they gave me a sample size of the #108 for interior. I just tried it yet yesterday. Sprayed down with the usual megs interior spray detailer then i used this and applied a coat. Well looks nice and good, but when i went back in my car the next day it smelled horrible. Worse than a chemical smell. I like the smell that megs interior detailer gives off. Anything else better than this. Really was not a difference to the megs, not looks like prob added on protection though. I'll try aero 303 or something, but then again if i clean interior weekly do i even need extra protection than just megs interior detailer?