HSS-Proff drills are the most common as they can be used in most materials. They are suitable for hand machines as they can withstand relatively high speeds and normal tightening. Manufactured in accordance with DIN 338 for high precision tolerances and geometric accuracy The HSS-Proff drill bit is made of high quality steel which extends its life The drill bit is ground at 118° The spirals are ground and angled at 30° to ensure effective chip removal Black oxidized finish Manufactured in accordance with DIN 338 for high precision tolerances and geometric accuracy Suitable for hand machines Fastening: Cylindrical neck Recommended for the following materials: all types of wood, aluminum, brass, copper, sheet metal, mild steel, plaster and plastic. HSS Drill Set 170 pieces Contains : 10 pieces of each 1.0, 1.5, 2.0 , 2.5 ,3.0, 3.5 , 4.0, 4.5 , 5.0 , 5.5 , 6.0 , 6.5 , 7.0 , 7, 5 , 8.0 mm 5 pieces of each 8.5 , 9.0 , 9.5 , 10.0 mm This drill set is made to the highest quality and our huge volumes allow us to sell it at a price far below all others. Maximum performance and quality at the lowest prices on the market.