Specification:(1)2pcs 13mm Straight Shank Twist Drill BitsCutting Edge Diameter : 13mm / 0.51"Shank Diameter : 13mm / 0.51"Cutting Edge Length: 102mm / 4.02"Shank Length : 40mm / 1.57"Total Length : 150mm / 5.91"Material: High Speed Steel 4341Finish: Black & Gold Oxide FinishShank Type: Round ShankType: Hot RollingDescriptions:1. High-speed steel tool is good for most general purpose applications, featuring a combination of hardness and toughness for wear resistance2. Reduced shank drill expand the size range capacity of a portable drill chuck. Common flute and overall length for minimal adjustment during tool changes.3. Premium gold titanium and black nitride dual coating can apply lubricant better for smoother drilling and is more durable and corrosion resistant than the regular black surface.(2)1pcs 3mm-13mm Step Drill BitSurface Treatment: Titanium CoatedMaterial: High Speed SteelShank Size: 6.3mm / 0.25 inchStep Quantity: 11Total Length: 76mm / 3 inchesCutting Diameters: 3mm,4mm,5mm,6mm,7mm,8mm,9mm,10mm,11mm,12mm,13mmMaintenance Tips:1.Not for hammer drill.2.It is recommended to oil the bit before every use.3.Please drill a smaller hole to make drilling smoother.4.Please do not set drilling speed too high to avoid damages to cutting edge.5.The metal sheet on which you want to drill should not exceed 0.38” in thickness.6.Check the concentricity of the spindle and spring chuck and the clamping force of spring chuck, for it may cause the drill bit broken and make drill hole too large.