What Is the Name of This Tool?

Allen keys or Allen Wrenches are also called Hex keys.  Hex keys are made to drive tools and screws with a hexagonal socket in their heads. Allen Keys are formed of a single piece of hexagonal rods of hard steel. They have blunt ends that are meant to fit perfectly into the screw’s socket. These keys are twisted in “L” shape with uneven arms. The concept of Allen keys appeared in the 1800s and became famous. Allen keys come in various sizes which are measured by across-flats (AF).