After buying a dremel 8000, the base includes a drill is 3.5mm. It is too big for all small jobs so this drill kit is essential. Be careful because the drill is 0.4 necessarily fragile. As against these bits are not used in the basic chuck that accepts only 3.5mm. This must be taken: Bosch Dremel chuck from 0.4 to 3.4 Order both sets or go in store they will be less expensive (found it this weekend).