If you have many different size/type ring spanners in your toolbox or tool bag, it's best to keep them together and organized if you don't have enough space for fancy filing. The pins fit wrenches up to 1/4" and 7mm. Are there SAE, metric, combination, dog, offset, short? You'll be surprised at how comfortable they are and how quickly you'll use most of the 20 included, and DIRTY CHEAP compared to other accessories to keep your keys handy and tidy.