The 3" sanding disc can be used for sanding on headlights that have severe discoloration. Once the initial sanding is completed with the 180 grit, resume the regular sanding procedure using the:
320 grit sanding discs
500 grit sanding discs
800 grit sanding discs
1200 grit sanding discs
1500 grit sanding discs
followed by the 3000 grit polishing disc.