Premium orbial sanding discs provide excellent sanding performance on wood, metal and plastic. Industrial aluminium oxide (AO) offers a great combination of strength, hardness and durability. Hook and loop system for quick removal. Grit size determines the smoothness of the finish. The higher the grit the finer the finish. Compatible with most brands of finishing sanders. Each sanding disc has 8 dust extraction holes for a safer working environment (when dust collector/extractor is present) How Do I Know What Grit of Sandpaper I Need The grit you use depends on what job you are trying to do. The lower the grit the rougher the sandpaper and conversely, the higher the grit number the smoother the sandpaper. The table below gives you an idea of what grade you may need for your application. Grade of Grit Common Name Uses 40-60 Coarse Heavy sanding and stripping, roughing up the surface. 80-120 Medium Smoothing of the surface, removing smaller imperfections and marks. 150-180 Fine Final sanding pass before finishing the wood 220-240 Very Fine Sanding between coats of stain or sealer. 280-320 Extra Fine Removing dust spots or marks between finish coats 360-600 Super Fine Fine sanding of the finish to remove some luster or surface blemishes and scratches.