Steel: 31CrV3 47-52 HRC Chroming H: 50 mm Length: 175 mm An Allen wrench (also known as a hex key) is used for working with fasteners that have an internal hexagon. Angle keys combine two levers in their design: an elongated one for applying maximum force and a short one for quick rotation. They are also used for working with fasteners in restricted spaces. The high strength characteristics prevent damage to the edges of the fasteners. You can also buy a set of hex keys.