This drill bit set has 4 sizes, including 6/8/10 and 12mm to meet your various tasks. The carbide is of high quality with a reinforced head that is not easy to rust and wear. The drill bits have high hardness and wear resistance. The triangular tip of the drills prevents walking or slipping. The groove drilling design can be very effective in removing debris. The drill bits are smooth without uneven edges. The set is ideal for drilling into concrete, brick, wood, plastic, soft metal, masonry and drilling fixing holes in bathroom tiles or wall mirrors. Attention: When you are going to drill hard materials such as glass, ceramic tiles, marble, we suggest you use water for cooling, which will avoid breakage and ensure the drill bit has a longer life.