Specifications: 4 Pcs set includes bits for drilling pilot holes for screw sizes #6, #10, #13, #16. You can drill the screw hole and the counterbore that holds the screw cap at the same time and keep both on the same axis. After the screw is screwed on, the screw cap is below the plane of the board. Suitable for drilling machines with chucks or joints. Suitable for drilling on hard wood and wood layers. Type: Countersink Drill Bit Material: HSS Handle: 1/4 Hex Shank Features: Tapered, Durable, Hole Cutter, Hex Shank Size: 6#: 3mm/0.12", 10#: 3.5mm/0.14", 13#: 4mm/0.16", 16#: 4.5mm/0.18" (Approx.) Notes: Due to the light and screen setting difference, the items color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Package Includes: 1 Set of Countersink Drill Bit (4Pcs) 1 x Wrench