The description indicates that these are regulation size at 3.93 inches. Tournament grade Bocce ball sets are available with 100 mm to 115 mm diameter balls. BUT... Bocce Standards Association has chosen the International Standard ball diameter of 107 mm (4.2 inches) and weight of 920gms. (2 lbs.) as the standard size. 3.93 inches equates to 99.82. These are not quite regulation size. If you are looking to have fun and just play, then go for it. If you want true regulation, then keep searching.