I just bought a Duffy the other day and lucky for me the glass was on it was perfect... and I intend to keep it that way. I called up the Duffy service guys and asked them what they use to keep them looking good. They recommended Meguiars 10, 17, and 18, so naturally I decided to stock it in the store. It'sll help keep up isinglass, plastic, plexiglass, lexan, and polycarbonate windows. $8.95 and a little due diligence sure beats the $3,500 they charge for a set of new windows!