Durable Material: These diamond drill bits are made of high strength carbon steel with nickel plated surface, to extend the service life. The cutting piece at least six months to one year before grinding. Clean and smooth cutting: the diamond hole saw is coated with high quality uniform diamond to increase the drilling speed and precision, can cut smoothly without broken edges to achieve excellent cutting effect. 10 Different Sizes: The drill bit set contains 10 different sizes: 3mm, 4mm, 5mm, 6mm, 8mm, 10 mm, 12mm, 18mm, 32mm, 50mm. Quantity and size are enough to meet most of your different needs. Side Opening and Laser Marking: With the side spline hole design, the drill bit can remove the scraps to keep the bit clean; With laser marking, the size mark will be more clear and durable than others, and not easy to wear. Wide Application: The drill bits can be used with standard electric drill. Widely used in marble, porcelain tile, glass, tile, jar block, granite and so on. When cutting hard materials, please use lubrication (water) to prolong the service life. Contents: 10 diamond drill bits