3 4 Piece Carbide Tipped Porcelain Drill Bit Set Size 10mm This carbide drill bits will drill anything including porcelain, glass, different types of tiles, ceramic and other hard fragile materials without chipping or cracking the material when properly used. Speed should be MAX 800 RPM using a steady, moderate hand feed. This drill bit is very sharp and will easy start on soft and hard materials. Dry or Wet use. When used dry - do not overheat and do not put extra pressure on bit. Use of coolant is very important and will increase drilling speed and working life. If you need other sizes - please check my other listings. If you interested to buy come quantity - please contact us and we will combine postage and will adjust price depend of quantity. for more information please visit www.diamondtools.ie