The slightly bigger ball used in USGA-governed territories became known as the "American ball," while the smaller ball used in R & A areas was known as the "little ball," "British ball," or "British Open ball." (For good measure, it was also known as the "European ball.") Actually, the American ball is actually larger than the little ball, but only by about 1 millimeter. This isn't enough to make a difference for most shots, especially since both balls are nearly identical otherwise. There are some regions where they use balls that are specifically designed for those tournaments. These balls are usually much harder and have more dimples on them than what's used in regular play. They're also usually white instead of blue. In fact, there are even competitions where the used ball can be marked with tags to indicate which company made it. These balls are then put away in the museum case after use. But other than that, there's not much difference between the balls used in Europe and here in the United States.