15 Sizes: 15PCS Drill Diameter has 6/8/10/12/14/16/18/20/22/25/26/28/30/40/50mm. Diamond drill bit for glass, ceramic tile bottles, block glasses, ceramics, marble stone slabs, perforated granite and other hard surfaces (especially glass and ceramics). Materials: Diamond drill bit is made of high quality natural diamond sand and hardened by special electroplating technique. Note: Our drill bits are not suitable for use with microcrystalline materials of any surfaces and tiles. Advantage: Nickel-plated diamond dust coating provides excellent performance and cutting resistance, no damaged edge, no vibration phenomenon, low cutting resistance, fast opening speed, easy chip removal, etc. Operation: Drilling with diameter can be used to cut diagonal holes, create circular bond and drill the hole to the right. water must be lubricated while drilling. Note: Reduce the speed of the diamond tip, low drilling pressure. If you have any questions about the quality of our 15PCS glass drill bits,