[Cobalt Drill]: Crafted; made of M35 material, 5% cobalt content, hardness high and stable performance. Cobalt steel can prolong cutting edge life and maintain cutting life after resharpening. age of stainless steel, cast iron, sheet metal, thin steel plate and angle iron. It is widely used. for drilling plates of stainless steel, carbon steel automotive spring and steel matrix.^[Easy to to use]: the split point at 35 degrees begins immediately at drill, with less force, thus eliminating the « trampling » on the working surface.^[Professional Drill Bit]: High surface finish, high grinding precision, sharp and durable blade. It is an effective professional exercise.^[Size available]: There are 10 different sizes to choose from to meet your needs. your different needs. Drilling Size (Optional): 1.0, 1.5mm, 2mm, 2.5mm, 3.0mm, 3.2mm, 3.5mm, 4mm, 4.5mm , 5mm.