STRENGTH & HARDNESS: High Speed Steel (HSS) along with bright finish ensures outstanding durability and sharpness, can reduce the friction. Size includes 2 mm to 8mm***2 FLUTES FORM & ROUND SHANK: 2 flutes form helps clear chips and debris away from the bit, decreasing friction and heat for a faster, cooler drilling process.***WIDE APPLICATION: The drill bit set is more suitable for processing materials, such as alloy steel, plastics and woods, and also can be used for softer materials.***Drill groove:Black Oxide treatment***Made of high quality carton steel,Hardness of working part of drill bit HRC50"***