Material: The countersink bits are made of 4241 high speed steel. 90 degree angle on tip for clean, precise milling. The cutting edge is hardened and honed for sharpness. 6-Piece Countersink Drill Bit: This flute countersink drill bit set is available in 6 different diameters. Size - 6.3mm, 8.3mm, 10.4mm, 12.4mm, 16.5mm, 20.5mm. Meet your different size needs。 One-piece design: The tapered surface processing can be completed in one go, and both sides of the drilled hole can be quickly cut and chamfered in seconds.< /p> Widely used: It can process all kinds of soft or ferrous metals, suitable for thin iron plates, insulation plates, aluminum plates, PVC plates, wooden plates, etc. with hardness less than 25HRC. Processing: Countersink drill bits are perfect for driving 90 degree holes in wood and countersunk screws and fasteners. Suitable for DIY, home and general construction/engineering. Note: The data are all manually measured, please allow 1-3cm error due to light and color