The dealer tried their own stuff that they said they use on all their convertibles. It didn't work. Might just be a defect in the plastic since "Z8Mania" indicated that the glass was totally transparent when he got his and this was not the case with mine. If the problem is a foggy plastic window, then some plastic polish might be what you need. I have tried the brand sold by Porsche and another sold by Griots Garage (www.griotsgarage.com I think). They seem to do the trick. Good luck!