The standard size of paper clamps vary from 1inch to 2inch, and these sizes are appropriate for bundling up A4 sheets. But if your sheet size is bigger, you can also buy a 3inch clip. The latter size is not very common, though. You will find many clips with attached characters on top like round smileys. These are usually 2inch sizes pretending to not look big while being clipped. Even if you go search various other paper clips types, you will see this is the standard size universally.