collar designed limits the penetration of screws to board and prevents damage to wall or boards by twisting screws over. strong chromium steel, which is wear resistant, and with high hardness.Suitable for gypsum board, woodworking board, drywalls and more. These bits help you fix the screw exactly in place without worrying about wobbling or misdirection. Speed up the process of twisting screws so you can work more efficiently and easily! The and designed allows the screw to attach to the bits without falling off, making your work easier and effortless. Widely suitable for electric screwdrivers, manual screwdrivers, electric drills, hand drills,, Manufacturer: buleerouy