Cobalt Drill Piece Set – contains 19 drill bits. Sizes are from 1.0 to 10.0mm by 0.5mm steps. Made from 5% cobalt alloyed steel, drill flutes fully ground, to DIN338 specification. They are particularly suitable for drilling difficult materials such as stainless steel and other very hard metals. It is important to use the correct speed for the drill size and the material being drilled as per the detailed chart on the back of the box.