have a 3.175mm shank. The cutting edge is 8 mm long. I can use them on a desktop CNC router to do fine detail work on lightweight materials and accurately drill tiny holes in printed circuit board (PCB) material, thin fiberglass, etc. I would not use them in my hands. held the device unless I was very careful. A small, high-speed rotary tool like a Dremel will do, but the small size means it's easy to break if there's a lot of lateral pressure on the bit, as the TC is stiff but not flexible. Figure 1 shows the box, 2-4 bits are closer. I recommend this brand TOPPROS 1.5mm/0.059" Carbide End Mill CNC Router Milling Cutter Circuit Board Cutter 1/8" Shank Pack of 10 very important. I hope you found the information and my review helpful.