Descriptions:1. Smooth and exact finish for lowering incision resistance and drill pressure, increasing the sharpness, and effectiveness of water lubrication.2. Produce clean and accurate holes in minutes with little or no chipping. The pilot-bit in the center helps for cutting accurate holes.3. White Zinc plating on the bits maximizes tool’s life with great resistance to corrosion. Excellent for making holes on glass or ceramic and considerably extending drill bit life.4. Diamond drill bits along with clearance hole facilitate the entrance of cooling water and escape of chips and other particles from drilling. Makes drilling process easier.5. Suitable for Stone, Tiles, Ceramics, Glass, etc Processing. Works better with a electric drill (Excluding in the item).Specifications:Drilling Diameter: 80mm / 3.15"，90mm / 3.54"; 95mm / 3.