Allen keys and hex keys come in a wide range of sizes and various types. The majority of people will find an allen key set is all that is needed in the toolbox, but occasional single allen keys are useful for specific projects.
Hex and allen keys are simply different names for the same simple tool. The often come in two measurement ranges - imperial allen keys & metric allen keys. Some have long arms for extra leverage and hard-to-reach places. Ball point or ball end allen or hex keys have a ball at the end which allows the key to be used at an angle or off-axis. Allen keys can also come with Torx heads.
See our full range of allen keys, hex keys, sets and singles from Stanley, Vitrex, Teng, Faithfull & Wera below.