I have been designing computer accessories for many years and recently looked at CD and DVD media. Specifically to prevent scratches to the media surface from mishandling from case to drive. When the CD is resting in the case there is approximately a .003 gap between the CD and and plastic bottom. Because the CD flexes it is possible to scratch the surface of the CD during removal. By filling the gap with a non-scratch material and a slightly raised cleaning bar you can fully protect the CD surface. I wrote more about this topic on my blog at this link, http://blog.save364.com/favorite-pr...-your-game-music-video-and-data-cds-and-dvds/