Featuring an extra-duty felt, the Penn Championship tennis balls ensure increased durability and excellent playability on hard courts. Approved by the United States Tennis Association and International Tennis Federation, they offer a controlled fibre release for a consistent nap. A great feel and reduced shock are provided by natural rubber, whilst an interlocked wool fibre delivers longer wear. The Penn Championship are the official balls of USTA league and come in a pack of 1 dozen (3 x 4-ball tube).