MATERIAL---Using high quality diamond, the drilling ability was better that the drilling hole is more accurate. 16PCS DRILL BITS---Comes with 16PCS different sizes of drill bits, including 6mm 8mm 10mm 12mm 14mm 16mm 18mm 20mm 22mm 25mm 28mm 30mm 35mm 40mm 45mm 50mm WIDE USE---Widely used in glass, ceramic, marble and other brittle hard materials. DURABLE --- The drill bits are made of 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 (dry drilling is strictly prohibited). Package Included:1 Set of 16 Diamond Drill Bits