You can use a baseball of any size or material for a makeshift or fun game of baseball, but in regular competition you must use official baseballs. Most levels of play have their own official balls made to specification; children use different balls than college players etc. Major Leaguers use baseballs designed for wooden bats, while many other leagues are designed for aluminum or composite bats. A baseball is nine inches in diameter and weighs five ounces, but youngsters often use smaller or lighter baseballs. Traditionally, baseballs are made of a wool or a cotton thread wound tightly around a center core of cork, which is surrounded by rubber. Baseballs are then covered by leather or synthetic material and glued and stitched together to create seams, which are raised, rolled or flat. Hollow perforated plastic balls are often used in practice as are softer safety balls.
