Wiffle ball is a variation of the sport of baseball designed for indoor or outdoor play in confined areas. The game is played using a light-weight plastic perforated ball and a plastic bat.
According to the Wiffle Ball Association of New Jersey Rule 2.00: THE BALL: Only the white baseball size Wiffle®Ball, (eight slots on one side) will be used for play.
The USWA will allow the ball to be scuffed with sandpaper, etc. prior to the start of the game and between innings only. Two to three balls should be brought to each game. If a ball is torn more than 1/4 inch it will be ruled illegal for play and will be removed from the game. A ball may be kept exclusively in the possession of a pitcher as long as it is ruled legal. No foreign matter can be added to the ball.
Note: Other associations suggest using a new ball at the start of each game, the USWA feels some pitchers prefer using their own ball.
NJ Wiffle Ball Association – http://www.wiffleballusa.com/rules.html
Photo – http://www.timesunion.com/sports/article/Wiffle-Ball-dream-comes-true-1396467.php