Baseball ball : A baseball is the type of ball the game of Baseball is played with, and named after. 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.