Specification Package: 10Pcs 5mm Twist Drill Bits Material : High Speed Steel M35(HSS-M35) with Cobalt Color: Champagne Shank / Cutting Edge Diameter: 5mm/0.2inch Blade length: 52mm/2inch Total length: 86mm/3.4inch M35 Grade Cobalt Steel 1. Cobalt drill bits are made of steel alloy with certain percent cobalt. 2. The 5-percent alloy is known as M35 grade. The cobalt increases the strength of the steel and makes it more heat-resistant. 3. Jobber length twist drill bit's hardess is uniform throughout the entire material, so that can be repeatedly sharpened without damaging the cutting edge allowing it to drill more than hss drill bits. How to Use Twist Drill Bits? 1. Ensure the left and right cutting edges of the drill are symmetrical when drilling. 2. Observe the uniformity of the spark while drilling, adjust the pressure in time, and pay attention to the cooling of the bit. 3. Mini twist drill bit can NOT be used in the impact drill. 4. Please use with cooling liquid to prolong the working life of the drill bits and to avoid overheating and breakage. 5. Drilling metal is recommended for use on bench drills. 6. Hand drills are suitable for drilling low hardness materials. Kindly Note: Please allow 1-2mm errors due to manual measurement, thank you for your understanding!