Professional Hole Cutter: With special brazed diamond design for porcelain, glass, marble, ceramic, rock 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 life: heavy duty hole saws offer superior performance, durability is more than 8 times Tips: The electroplated diamond coating wears off if the tool gets too hot. Never let your drill bit run dry. Package Contents: 6mm, 8mm, 10mm, 12mm, 16mm, 20mm, 22mm, 25mm, 30mm, 38 mm, 50mm