I am restoring a 56 Olds and when I purchased it the rear window had a thousand fine scratches and 75 scratches you could catch your finger nail on. Finding out that the glass was obsolete sent me on a several month search for a good replacement with no luck. I purchased the Eastwood glass scratch repair kit which is probably designed to remove a couple of bad scratches. I do a lot of body work so I am familiar with the use of a DA/Palm sander. Using my palm sander I started the process by sanding half the window at a time. I went after the deep scratches first then with long flat strokes I worked the whole window, keeping it flat I ended up with only two MINOR spots of distortion. I used a lot of disc and the hours must be over 100. BUT I have a beautiful scratch free, crystal clear glass to put back in my Olds.