Allen key in T-Shaped shape from F.F. Group company with a tip size of 21. A hex key is ideal for any type of use by any professional mechanic, plumber, carpenter, electrician, as well as for household use. Hex keys are formed from a single piece of hexagonal rod made of hardened steel with chamfered ends that fit comfortably into similarly shaped screw sockets. Due to its shape, it allows you to exert more pressure, making the work less tiring.