The sponge disc is gentler than the wool disc, and the cutting force is lower than that of the wool disc.
Sponge discs are also divided into rough thrown discs and reduction discs. The rough discs should be hard and are used with rough wax to treat scratches; the reduced discs are the softest and can be used with mirror treatment. The marks left by the rough wax treatment of scratches can achieve a mirror effect, like The new car is as beautiful as new.
The wool disk has a large cutting force and is generally safer to use at low speed. It is better to use when dealing with scratches. It is not recommended to use the wool disk for mirror restoration.