High quality alloy steel and HSS, sharp and durable to use. Can be used again after grinding. The alloy steel body features marked graduations on the beam for fast measurement and application. The hole diameter can be adjusted by the distance from the drill bit tip to the center. Hole diameter range: 40-120mm/ 40-200mm. Ideal for drilling of woodworking work,laminates, plastic,acrylic,  plywood,composite,plaster, rubber,and cardboard. Please apply only to thin boards.