SincereetaliPremium Quality: These countersink drill bits are made of high quality alloy steel. They provide superior cutting power. High hardness and wear resistance, convenient and quick to drill. 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 provided 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