The round sleeves are particularly well suited for round, curved, bulging or cup-formed shapes contacting hard to reach contoured areas, which before could only be done by hand sanding. They eliminate scratches and allow you to apply the sander's total width against the work piece or to use only the edge in all kinds of complex sanding. The sander actually becomes round when pressed against a round surface and flat when pressed against a flat surface i.e. the sanders conform to the underlying surface. Every sanding sleeve is custom hand made to specifically fit each inflatable round sander. To eliminate deep scratches or gouges, start with the coarse, heavy 60 grit working your way up to the fine 220 and extra fine 320 grit sanding sleeves for a final finish.