Material --- Using high quality alloy steel, the Drilling capacity is better than drilling and 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 bit is made of emery coating, ideal 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 (dry drilling is strictly prohibited). Package Included: 1 Set of 16 Drill Bits diamond-plated