An Allen key or Allen wrench is also known as Hex key. This is a small handheld tool used for turning bolts and screws which have hexagonal sockets. Many people assume that Allen keys are new, but to surprise, these tools are fairly old. The concept of a hexagonal-shaped screwdriver came in the mid-to-late 1800s and became popular. High grade alloy steel, heat-treated and tempered for added strength and durability. Rust and corrosion resistant surface. Keys with size marking for easy of identification. Tamper proof.