The C115COMBC set of 115 drill bits covers a wide range of drilling jobs and consists of: R10CO sizes 1/16? to 1/2" in 1/64? increments, R18CO in sizes from N1 to N60; and finally R15CO sizes A to Z. All drills in the set are manufactured from premium High Speed cobalt and can be used for drilling tool steel and other hard materials, whilst the 135 degree split point is an aid to self-centering and reduces the amount of force needed to drill the hole. The drills have a heavy duty design which is recommended for use in difficult materials and applications. With a bronze oxide finish to prevent workpiece material from sticking to the cutting edges of the drill, you can be sure of accurate holes with the C115COMBC set.