Designed to replace fragile stone discs. Fits Dremel and other hobby drills.Use to cut piano wire, perspex, all composites, woods, ceramics, stone and vacuumed formed mouldings etc. Running speed 5,000 - 20,000 RPM. Use at 10,000 RPM and slower for cutting perspex, plexiglass, lexan etc. Will not chip or crack material. Recommended by EAA workshops for cutting aircraft canopies.