12 Pcs,1/4", Black And Gold Coated Twist Drill Bits, Pack In Plastic Bag High Speed Steel: Twist Design: Notice: Please keep cool and gentle using, the working life of the twist drill bits can be largely prolonged by proper usage. Bright finish: Classic M2 High Speed Steel construction with Bright Finish for proven capability and durability. Strength Hardness: Made with HSS M2 steel, Rock wall Hardness Level HRC 62-63. Package Size: 12 Pieces in a plastic bag, Diameter 5/16 inch, Total length 4 inch, Working length 2-3/4 inch. Professional DIY Use: For use on metal, wood plastics. Not For Use On Concrete / Masonry / Stainless Steel. Perfect match for workshop or service vehicles. 135 Tip Twist Design: Increases cutting speed with self-centering and prevents walking, clears chips and particles faster.