This single drill bit can be used for drilling a wide range of hole sizes from 3mm to 13mm. Step Size: 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm. Hex Shank: 1/4". The step drill bit is made from high speed steel of high hardness and good wear resistance.
eBay