6 different diameters available:: 1.5 / 2 / 2.5 / 3 / 3.5mm. Each size has 20 pieces, 6 sizes can meet your different needs. Twisted spiral design, easy to remove sawdust, iron filings in the work. The twist drill is stable and sharp, the HSS steel is fast, and the long cutting edge makes the deep hole deep hole High speed steel, durable titanium surface treatment, improve the surface quality of the drill, reduce the friction coefficient with the workpiece, improve wear resistance. Suitable for all kinds of surface drilling, including aluminum, iron, wood and plastic, and is very suitable for DIY, craft projects and general construction applications.