Professional Kit: There are 20 different shapes and sizes of rotary burrs, you can choose different types of cutting heads according to the needs of the work, they will satisfy your different craft creation needs. Multi-function: Diamond drill bits have 10 different grinding bits for abrasion, carving, cutting, polishing and engraving. Compatibility: 1/8" (3.1mm) shank, 39mm length, fit for dremel electric rotary tool and most mini grinder. User-friendly design and easy insertion process, incredibly easy to use. Quality Material: The milling bits are made of quality high-speed steel with long life, has the advantages of high hardness, good wear resistance and heat resistance. Shank Diameter: 1/8" (3.1mm) Total Length: 3/4"(40mm) Box Contents: 20 X Rotary Burrs 1.When using drill bits, the material temperature will be very high, please add water or coolant to avoid being burned. 2.For better tool protection, perfect for wood, plastic and materials has not so high hardness, it is better not to apply to stone or other hard material which may reduce the using period.becomeveryrich