Drill size tag: : 5-35mm(5mm . 7mm .10mm .12mm .15mm .17mm .20mm .22mm .25mm .27mm .30mm .32mm .35mm). A variety of drill bits can meet your different needs. thus saving time and money. Premium materials: : These tagged drill bits are made of heat treated 4241 high speed steel (HSS) and coated with titanium nitride. Titanium coating can reduce friction and operating temperature. which can effectively prolong the service life. Ladder structure: : The drill bit can drill holes of different specifications without purchasing multiple drill bits. thus saving space and money. Double groove: : automatic burring when drilling. Faster and smoother cutting. Three flat handles ensure a firm grip. Triangular round rod: can be easily installed in an electric screwdriver. a drill bit and a pressure drill. Applies to: : the set of tagged drill bits can be used for workpieces with a hardness of less than 25 and a thickness of less than 5 mm. Suitable for various materials. such as carbon steel. iron sheet. the insulation board. the PVC panel. the wooden panel and the wood. etc They also help enlarge existing holes and are not recommended for stainless steel.