A screwdriver bit is a tool for driving screws and one that can be fitted to most drilling power tools. All screws have a head with a contour such that an appropriate screwdriver tip can be engaged in it in such a way that the application of sufficient torque to the screwdriver will cause the screw to rotate.; ; Brand Name: Best Way Tools Drive Type: Phillips Size: #2 Length: 2 in. Product Type: Double-Ended Screwdriver Bit Material: Carbon Steel Number in Package: 150 pc Impact Rated: No Shank Type: Hex Shank Shank Diameter: 1/4 in. Packaging Type: Jar Magnetic: No