The pre-radiused concave luthier disk is for sanding guitar sides to contour the back and top radii. The unit is 24 inches in diameter. This is a must have for the serious luthier; it will help you be a better builder. Recommended for use with Blues Creek Guitars adhesive sandpaper in 60, 80, and 100 grits; sold separately.
See the tutorial section to see a simple jig you can make to do this task accurately.
this is for a 28-foot disk