This block lets you sand curved surfaces such as helmets with ease. I cut up an old sanding sponge to fit inside the lower disk as it conforms to my helmets when sanding. I needed a way to easily and comfortably sand helmets and so I made this. I included steps on how to load it but basically I just cut out a square of paper and screw on the grip. Works pretty well and stops my hand from cramping. Works with 120 to 600 grit and probably more that's just what I use.