Professional Diamond Hole Cutter: With special brazed diamond design for porcelain, glass, marble, ceramic, stone and granite, etc. High Quality Hole Drilling: Made of carbon steel with diamond blade, ideal for drilling clean, precise holes and cutting perfect circles with these tools. Long Lifespan: Heavy-duty hole saws offer superior performance, the durability is more than 8 times. Tips: The electroplated diamond coating will wear out if the tool gets too hot. Never let your drill dry out. Package includes: 11-piece diamond drill bit set 6 mm, 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 22 mm, 25 mm, 30 mm, 38 mm, 50 mm