It's easy to do and it work pretty well.
Step 1: YOU NEED
-an empty candy box;
-bike inner tube;
-different n° of sanding paper;
Step 2: CUT THE INNERTUBE
Step 3: CUT THE SANDING PAPER
Wrap it around the top part of the box, on top of the inner tube, really tight.
Close the box.
Step 4: CUT MORE SANDING PAPER
Fold them and place them in the box.