Premium Quality: These taper drill bits are made of high quality alloy steel. They offer superior cutting power. High hardness and wear resistance, convenient and quick to drill hole Various Sizes: The drill bit sets include 5 kinds of sizes: 2.8 x 8mm/3.0 x 8mm/ 3.2 x 8mm / 3.5 x 8mm / 4 x 8mm. Removable and adjustable: use the included wrench to remove the screw and adjust the length of the countersunk hole to adjust the drilling length of screws of different lengths. These drill bits are a great helper in our daily life and improve your work efficiency. Multiple uses:: used for wood, plastic, soft metal, fiberboard, aluminum alloy screw cutters, holes, etc. Function: faster cutting and chip removal, no need to replace the drill bit to achieve fast and smooth countersinking