Package includes: 13 drill bits, respectively: 3/4/5/6/7/8/9/10/11/12/13.5/14/15 mm This set of drill bit loses its hardness as a cutting tool once the tip starts to heat up. Using the hss drill at lower speeds with coolant or lubricant, you can successfully drill a large number of holes in metal. (continue to add water for cooling while drilling). Our drill bits with low tungsten content are not suitable for stainless steel, aluminium alloys, coloured steel and other hard metals, but are suitable for a wide range of aluminium alloys, iron, copper, brass, wood, plastics and other metal materials for hand drills, bench drills and more. Our drill bits bits are available in 13 different sizes to meet the various needs of your work, no need to buy other sizes separately, one set of drill bits can meet most of your drilling needs. Carbide drill bits are mainly used for pig iron and cast iron. Carbide drill bits have high toughness, abrasion resistance and hardness for high speed cutting, with a large piece of carbide at the end of the drill, allowing you to easily complete your work at high speeds. B07HG51HJ2