回复：There are many kinds. They are disk polishers. The one you a

called "Skipdoctor CD Repair Kit", I believe. Plastic disk (base material) in CD is clear, and like a Laser beam goes through this plastic disk to read data from metalic coating on the other side where your data reside. CD polisher is used to polish this "window" so that laser beam can see through properly.

Motorized one works better.

I hope this helps.

Best regards,

Alex