The mass of a baseball is about 145 grams or approximately 5.11 ounces. According to the Major League Baseball website, an official baseball cannot weigh less than 5 ounces or more than 5.25 ounces.
For circumference, a baseball must be between 9 and 9.25 inches around, according to the Major League Baseball's official rules. A baseball has a core of cork or rubber. Yarn surrounds the core, and each baseball has 369 yards of yarn in increasingly lighter weights as it goes towards the outside of the ball. The final layer is made of leather. Both the yarn and leather are tightened around the core and affixed with the iconic 206 stitches.