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Allen keys are one of the most important tools a cyclist can own. But there are so many types, right do you use? Below are they varying types of allen keys – and who needs them.

T-Handle

Popular in motorsport applications, the T-handle acts as a balanced weight to help you spin the wrench quickly, while allowing enough leverage for common usage. Some areas of the bike won’t suit a T-handle (such as adjusting most seatposts) while cranks and pedals will often be too tight for common T-handles. Beta 951 wrenches, which allow the T-handle to slide into a position to create an L-style tool, are an exception. These are quickly becoming the choice of many professional road and mountain bike mechanics, but at over US$20 per wrench, they’re items best suited to those who get a financial return on their tools.

P-Handle

This type of Allen key, made popular by Pedros, Park Tool and others, is something I see lots of in professional workshops. It’s effectively an oversized L-wrench with a comfortable grip at the bend that gives it similar benefits to a T-handle. I’ve used these for many of my wrenching years — they’re a solid choice and only rare instances, such as seat clamps, will call for a different style.

Three-Way

Park Tool made this style, which places three of the most common sizes into one tool, famous… and mechanics around the world still naturally reach for it. Many brands now offer two or three different sizes of three-way, but the standard four4, 5 and 6mm three-way remains the gold standard. Much of a bike can be built with this one single tool. Sadly, however, the limited length and triangular shape means it’s a poor choice when working with tight clearance. Installing bottle cages, adjusting a saddle or even just adjusting a disc brake caliper will prove slow, if not impossible.

Folding

Effectively what multi-tools are based on, you can get a full set of Allen keys as a folding set with the storage doubling as the handle. This ‘Swiss-Army knife’ of bicycle wrenching is popular with some mechanics, as they rarely need to reach for other tools. Of course there are many downsides including a general lack of leverage and clearance. Out of all the styles mentioned, this is the only one I don’t use in the workshop, but I do keep one in the car.

Ratchet

Ratchet Allen keys are available in a few different varieties. The best ones for bicycles use replaceable bits instead of actual sockets, keeping the tools’ profile shallow. A ratchet offers significant speed benefits, but will require swapping between different-sized bits. While it’s possible to do most of the bike efficiently with a ratchet, I keep a PrestaCycle ratchet handy only for fiddly items such as saddle clamps. Additionally, the bits of these ratchets can be used in an electric drill driver. This is certainly something that can do more harm than good when used incorrectly, but it’s a popular choice when working with rotor bolts (commonly a T25 bit) and other repetitive tasks.