Definition: For decades, there were two different minimum sizes of golf balls in the golf world: There was the minimum size approved by the R&A, and the minimum size approved by the USGA. The USGA's minimum size was very slightly larger than the minimum size approved by the R&A. The larger ball played in USGA-govered areas became known as the "American ball," while the smaller ball golfers in R&A areas had the option to use was known as the "small ball" or "British ball."
The two governing bodies agreed that the weight of a golf ball should be 1.62 ounces. But in the early 1900s, the R&A approved golf balls with minimum diameters of 1.62 inches. In the early 1930s, the USGA ruled against those smaller balls, sticking with a minimum diameter of 1.68 inches.
The different rulings on golf ball sizes existed until 1990, when the diameter was standardized at 1.68 inches. See "British Ball" for more details.
