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
- The Official Site of Major League Baseball
- Minor League Baseball
- BASEBALL HISTORY Major League Baseball Players Alumni Association.
- Hall of Fame National Baseball Hall of Fame and Museum, Inc.