Steel: 31CrV3 47-52 HRC Chromium plating H: 30 mm Length: 105 mm An angle hex key (also known as an "Allen key") is used to work with fasteners that have an internal hexagon. Angle keys have two levers in their design: an extended one for applying maximum force and a short one for quick rotation. They are also used when working with fasteners in confined spaces. High strength characteristics help prevent damage to the edges of the fasteners. You can also buy a set of hex keys.