1/4" Shank Sphere 1" (Coarse Grit) Rapid yet controlled stock removal Easily smooths the hardest stock Use on Wood, Foam, Epoxy, Acrylics, Soap Stone, Silicone, Plastic, Polyurethane, Graphite and more Not for use on METAL or CERAMICS Recommended Operating Speed: 4,000 to 25,000 RPM