150-Grit sanding discs are a fine sandpaper for a final sanding pass before finishing. Fine grits like this are all used once the majority of the sanding is done. Its tempting to buy coarse 60 or 80-grit paper to speed up the sanding job. However, because modern lightweight joint compound is so soft, heavier grit sandpaper is not a necessity. Coarse-grit paper may have a tendency to leave undesirable sanding marks. We recommend 120-grit or 150-grit paper for the best results.