Have you ever wondered how a tennis ball is made? Watch this very well done video by Linn Tall to find out. There are approximately 70,000 tennis balls used each year at the U.S. Open. The reason so many balls are used at top tournaments is to ensure the fuzz quotient remains constant, because worn balls tend to travel and spin much faster. Did you know that men use different balls than the women during their Grand Slam matches? The men compete with an extra-duty felt ball while the women compete using a regular-duty ball. This is intended to speed up the women's game and slow down the men's.