A standard bocce set consists of 8 bocce balls and a pallino.
Typically there are 4 green bocce balls & 4 red bocce balls. People who are color blind complain about the typical red and green balls. You may want to get 4 dark colored balls and 4 very light colored balls. Every ball must be the same diameter, same weight, and made with the same materials, generally a hard plastic composite.
All 8 bocce balls shall be identical in size and weight. Tournament grade bocce ball sets are available with 100 mm to 115 mm diameter balls. The U.S. Bocce Standards Association has chosen the International Standard ball diameter of 107 mm (4.2 inches) and weight of 920gms (2 lbs.) as the preferred size.
The pallino (sometimes called the jack) is a small ball of contrasting color (usually white or yellow) used as the target ball. It is also made of hard plastic composite material. Tournament grade sets are available with pallinos from 40 mm to 60 mm diameter. The International Standard is 40 mm (1.6 inches) diameter. The most popular size in the U.S. appears to be the 50 mm (1.97 inches) diameter pallino. Pallino size is much less important than the bocce ball size and a strict standard size/weight/material is not usually specified.