We in cycling work with more internal socket than external hex screws. That's the trend, for sure. Wrench maker Wera is legendary for its Hex-plus™ allen wrench design. While there are many fine makers of internal hex keys, Wera's 1997 patent covers a feature no one else offers. It's rather simple, especially if you've examined external socket wrenches where features like Snap-On's flank drive is common—keep the turning load from landing on the corners of the hex. Wera has reversed the idea and the internal allen key has features to keep torque off its corners. See this discussion of the topic.
Bottom line: 20% more torque can be delivered to an allen screw before deformation. If you're skeptical, sacrifice a few allen screws to see the effect. It is easy to confirm. No wonder Wera are some of the most popular tools in professional boxes, especially today with a proliferation of fasteners often made crudely and of too-soft materials. We offer nine sizes of Wera ball point, long L keys in their steel, black laser model. Each key is hex-plus at both hex and ball ends, and bears a laser etched size inscription.
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