Perma Grit rotaries have an integral arbor, enabling them to be used in reversible drive tools. The arbor diameter is 3.1 mm (1/8”) and designed to fit Dremel, Proxon and Flexi-drive drills. They allow the user to cut a wide range of materials, quickly and cleanly, leaving an excellent finish. All rotaries are ideal for routing, shaping and removing materials, without tearing or clogging. Use on all Woods, Glass Fibre, Carbon Fibre, Kevlar, Plexiglas, Lexan, Perspex, Acrylics, Plastics, Polystyrene, Ceramics, etc. Excellent on Perspex, Plexiglass and Lexon. Below 10,000 RPM they will not melt, crack or chip these materials. (Not recommended for use on metal).