''' Baseball ball ''': The baseball’s core is made of rubber and cork. Yarn is wound around the rubber and cork centre. Then 2 strips of white cowhide are sewn around the ball. Official baseballs must weigh 5 to 5 1/4 ounces and be 9 to 9 1/4 inches around | ''' Baseball ball ''': The baseball’s core is made of rubber and cork. Yarn is wound around the rubber and cork centre. Then 2 strips of white cowhide are sewn around the ball. Official baseballs must weigh 5 to 5 1/4 ounces and be 9 to 9 1/4 inches around |