More info about the baseball sized Whiffle ball: Whiffle ball products regulation sized Whiffle ball. 9" In circumference. It's easy to throw curves with! to curve and control the ball follow the simple instructions as indicated on package. The Whiffle ball was designed to take the place of baseball, stickball and softball for boys and girls in back yards and city streets. It is made of a tough rubbery plastic is light in weight and cannot be thrown or hit any great distance. The Whiffle ball is also an excellent indoor ball. Safer fun. Indoors and out! Fun to throw , fun to bat and fun to curve.