Black binder clips commonly come in multiplesizes, which are mini, small, medium and large. Various brands may label the sizes of binder clips slightly different, such as micro instead of mini, as noted on the Staples website.
Different-size binder clips are used according to the amount of paper that needs to be fastened together. A mini clip holds as few as two sheets while a large clip can hold about 225 pages, notes Wilson Jones.
Louis E. Baltzley received a patent for the binder clip in 1915. Since that time, the style of binder clips has changed, but the structure and function remain the same as the original Baltzley design.