Carbide steel (45% carbide content). These bits are ground from a solid piece of metal instead of containing soldered on cutting edges; if you think the blades are not very sharp, you can sharpen them as you want easily. Made of high carbon steel, sharp edge, high hardness, accurate positioning, high precision, smooth cutting, impact resistance, high toughness. More smooth, less noise. A variety of sizes to provide a choice. Size: 15mm, 20mm, 25mm, 25mm, 30mm, 35mm (5/8-inch, 3/4-inch, 7/8-inch, 1-inch, 1-1/8-inch, 1-3/8-inch). It can be used for wood products perforation, mounted spherical door shoot tip, drawer, plastic products, wood, plywood, etc. It suitable for pistol drill, bench drill, vertical drilling machine hand held electric drill, stand motor-driven drilling machine and mobile ribbon type magnetism drilling machine, etc.