1、CHROME VANADIUM STEEL: Made of chrome vanadium steel, which has high hardness to ensure large torsion and good wear resistance. 2、GENERAL HEX SHANK: The shank is in common 1/4in (6.35mm) hex shape, which guarantees firm and tight clamping, and will not easily slip. 3、SELF LOCKING DESIGN: The anti dropping steel ball enables good fixing, and the self locking device is not easy to slip off, which is tightly fitted. 4、MULTIPLE SIZES: Including 11pcs tools in various sizes, and you can combine the multiple specifications for more flexible and efficient working. 5、GREAT PRACTICABILITY: Suitable for screwdriver handle or electric screwdriver tool to drive the socket, can fit to hex hole or three jaw chuck.