| 摘要 |
A device is provided for practice hitting a tennis ball, the device comprising a flexible pole adapted to be held in one hand, or fixedly secured in a suitable support, the pole mounting a retrievable line to the free end of which a tennis ball is attached. The ball is provided with a swivel element placed in the interior thereof. One end of the swivel element is attached to the wall of the tennis ball and the other end of the swivel element is attached to the retrievable line which extends through the wall of the ball at a point diametrically opposed to the point at which the other end of the swivel element is attached.
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