Description: These high strength HSS constructed drill bits are perfect for drilling workpiece with the hardness below 25HRC, such as for carbon steel, sheet iron plate, insulating plate, PVC plate, wood board, etc. Features: 4pcs HSS constructed drill bits for drilling holes with screw sizes #6,#8,#10 and #12. Special designed steel counter sleeve countersinks or counter bores hole. Adjustable counter sleeve depth with hex wrench. 6.35mm standard hex shank is fast change compatible. Drill and countersink for wood screws without changing bits. Drilling length can be adjusted for various length screws simply by loosening and tightening the setscrew. Suitable for drilling workpiece with the hardness below 25HRC, such as for carbon steel, sheet iron. plate, insulating plate, PVC plate, wood board, etc. Use on a drill machine with chuck or connector. Specifications: Condition: 100% Brand New Material: HSS 4241 Color: As Picture Shown Drill Size: #6, #8, #10, #12 6#: 2.38mm 8#: 2.78mm 10#: 3.175mm 12#: 3.56mm Hex Shank Diameter: 6.35mm(1/4'') Other Size: As Picture Shown Package Included: 4 x Drill Bits 1 x Hex Wrench . Note: Please note that the new type and old type of this product will be sent randomly, and make sure you will not mind before ordering.