The head adopts a brad point and two shouldered cutting spurs design, the brad point of the drill bit is mainly used for positioning, and the cutting edges of both sides serve as cutting***Drill groove:Black Oxide treatment***Cutting flutes are engineered for optimum chip ejection so drill will not bind and burn out.***Positioning accurately, punching / opening fast, sharp***Made of high quality carton steel,Hardness of working part of drill bit HRC50"***This professional wood drill bit set 5 pcs of Homdum Tools is ideal for drilling in wood Drill Sizes: 1 x 4mm 1 x 5mm, 1 x 6mm, 1 x 8mm, 1 x 10mm.