Here's the inside story: This is the first sander to adjust completely to underlying surfaces. It's ideal for sanding and polishing the interior of bowls, spoons, or any other concave surface. Stays soft all the way to the edge! Can be used on an electric drill, but works best on any flexible drive shaft that will accept a 7/32" shank size. Sanding sleeves are easy to change. They lock into position as the sander is inflated using a micro hand pump or a bicycle pump.