From our SPAX step drill 4, which consists of a 4 mm wood drill and a 6.5 mm countersink, you can quickly and easily assemble a perfect drill countersink. Simply put the two together and tighten the grub screw in the countersink with the Allen key provided. Side effect: This allows the drill countersink to be individually adjusted to your desired drilling depth. The wood drill bit can also be used individually. This means for you: No annoying change between drill and countersink, enormously time-saving installation of the planks.