100-Grit sanding discs are for smoothing of the surface, removing smaller imperfections, and removing marks. This grit is commonly used for most projects. In fact, it's best to start with this grit or higher and move up if necessary. It's 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, 150-grit paper or higher for the best results.