MATERIAL --- Using high quality diamond, the drilling capacity was better and the drill hole was more precise. 16 PCS DRILL BITS --- Comes with 16 PCS different drill sizes, including 6mm 8mm 10mm 12mm 14mm 16mm 18mm 20mm 22mm 25mm 28mm 30mm 35mm 40mm 45mm 50mm WIDE APPLICATION --- Widely used in glass, ceramics, marble and other hard, brittle materials. DURABLE --- The drill bits are made of diamond coating, which is great for drilling precise, smooth holes in glass or other fragile hard materials. NOTE --- By reducing the drilling speed and adding further water cooling to extend the life of the drill bits (dry drilling is strictly prohibited). Contents: 1 set of 16 diamond drill bits