US Patent 7331260 Rotary wrenching tool with a driving head

This invention relates to a driving head of rotary wrenching tools, the driving head can be a sleeve or directly implemented on the wrench, the driving head has an opening with grooves, forefront surfaces and concavities implemented inside the opening, the forefront surfaces are implemented individually in-between the grooves, and one concavity is implemented on each forefront surface, with which varieties of work pieces in different shapes can be tightly fitted into.