[50 sizes]: 10 steps: 1/4", 3/8", 1/2", 5/8", 3/4", 7/8", 1", 1-1/8", 1-1/4", 1-3 / 8" .12 Steps: 3/16", 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", 13/16", 7/8".9 Steps: 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4".13 Steps: 1/8", 5/32", 3/16", 7/32", 1/4", 9/32", 5/16", 11/32", 3/8", 13/32", 7/16", 15/32", 1/2".6 Steps: 3/16", 1/4", 5/16", 3/8", 7/16", 1/2". A variety of drill bit sizes are perfect for your needs [Premium Material]: These step drill bits are made of heat treated 4241 high speed steel (HSS) with a titanium nitride coating. [Ladder structure]: One drill bit can drill holes of different specifications, no need to buy multiple drill bits, saving space and money.[Special design:]: Provides faster, smoother cutting and a tri-flat shank ensures a firm grip. Triangular round shank: Can be easily adapted to power driver, drill and press drill. [Suitable for]: The step drill set can be used for workpieces with a hardness of less than 25° and a thickness of less than 5mm. Suitable for a variety of materials, such as carbon steel, sheet metal, insulation boards, PVC panels, boards and wood, etc. They also help to widen existing holes.Not recommended for stainless steel. Note: The data is all manual measurement, please allow 1 - 35cm error, due to the difference in light and display, there will be a certain color difference, depending on the physical object received.