[15 sizes]: 15PCS Drill Diameter has 6/8/10/12/14/16/18/20/22/25/26/28/30/40/50 mm. Diamond drill bit for glass, ceramic tile bottles, glass blocks, 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 all surfaces and tiles. [Advantage]: Nickel-plated diamond dust coating has excellent performance and cut resistance, no damaged edge, no vibration phenomenon, low cut resistance, fast opening speed, easy removal of chips, etc. [Operation]: Drilling with the diameter can be used to cut holes diagonally, create a circular connection and drill the hole to the right. Water should be lubricated during drilling. [Note]: Reduce the speed of the diamond tip, low drilling pressure. If you have any questions about the quality of our 15PCS