Steel: 31CrV3 47-52 HRC Chroming H: 40 mm Length: 145 mm An Allen wrench (also known as a hex key) is used to work with fasteners that have an internal hexagon. Angle wrenches have two levers in their design: an elongated one for applying maximum force and a shorter one for quick rotation. They are also used when working with fasteners in confined spaces. The high strength characteristics help prevent damage to the edges of the fastener. You can also buy a set of hex keys.