Features: Material: Made of high speed steel(HSS) with nickel plated, bit& 039;s tip head is 80-100 grit diamond coating, good abrasion resistance, high hardness and extreme, high quality and long service life Smooth Hole: Small resistance, center holes and side holes help to remove the waste, easy to cut clean and accurate holes, no broken edges 10 Size: 50mm/1.97inch, 40mm/1.57inch, 35mm/1.4inch, 30mm/1.2inch, 25mm/0.98inch, 20mm/0.79inch, 12mm/0.47inch, 10mm/0.39inch, 8mm/0.3inch, 6mm/0.24inch,diamond drill bit set with marked size, easy to recognize Easy Use: Work with all electric drill and impact drill, start diamond core drill bit, use less pressure Let your drill bit drill at it& 039;s own pace. Use plenty of lubrication/coolant to keep your drill tip cool and the hole clean Wide Application: Great for making your own glass crafts and projects, wine bottles, glass block, sea glass, tile, porcelain, ceramic, China, granite and more. Specification Material: High speed steel Color: Silver Size: About 50mm/1.97inch, 40mm/1.57inch, 35mm/1.4inch, 30mm/1.2inch, 25mm/0.98inch, 20mm/0.79inch, 12mm/0.47inch, 10mm/0.39inch, 8mm/0.3inch, 6mm/0.24inch Package included: 10pcs x drilling tapper Note: Due to the light and screen difference, the item& 039;s color may be slightly different from the pictures. Please allow 0.5-2cm differences due to manual measurement.