Play with the tennis balls that the best players in the world use! The extra-duty and regular-duty balls are made from a natural rubber construction that gives them a consistent feel, even during longer games, as well as a reduced shock. Surrounded by interlocked wool fiber for long wear, the controlled fiber release assures even more consistency in the balls. Deep elastic seams reduce the potential for cracking. Balls are available in cans of 3. Regular-duty balls are for use on clay courts.