What's the difference between a 28.5" and a 29.5" basketball?

29.5" (size 7) is the official men's ball used in the NBA, NCAA men's, and most high school boys' leagues. 28.5" (size 6) is the official women's and youth ball used in the WNBA, NCAA women's, and most middle school and girls' leagues. Players switching between sizes commonly report shot-distance recalibration is needed, especially from outside the paint.