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