The 30 Pc. Diamond rotary burr drill bit set is designed for use with rotary tools like Dremels. Each bit features a premium 120 diamond grit for medium cutting and comes in various shapes such as ball, needle, cylinder, and round head cylinder. With head sizes ranging from 1mm to 4mm and a 1/8" shank, this set is perfect for jewelry, watchmaker, and other precision cutting tasks. The overall lengths of the bits vary by shape and range from 45mm to 60mm to accommodate different applications.