Cheap Allen wrenches are just that, they will quickly round off and when they do they also round off the set screw. Expensive Allen wrenches have hardened tips that will not round off, most of those are brittle and are too easy to snap off. I like the Slot.it PA23 wrench, it has a clutch and the tip is a good quality. If you use the wrench a lot it will eventually round off. I like the wrench that Slot Car Corner sells, the tip does not want to round off and is not as brittle, so I have not broken one after a year of use. The tips are replaceable and you can even get your name engraved on the handle.