describe: Training tennis with a bungee cord. Put water, sand, or weights into the coach's baseboard so it's hard enough to hold the ball You don't need a tennis partner, you can practice tennis anytime. Especially to improve the tennis player's hitting, leg movement and hitting precision control. Tie the ball to the base with a rubber band without having to pick it up frequently. Unplug the base and fill the well with water or sand to keep the base stable on the ground. Avoid restricting sites, feel free to play or practice anywhere Suitable for white-collar workers, the elderly, teenagers, schools, entertainment venues, etc. Specification: Material: wool/rubber Each set includes: 1 tennis ball + 1 rubber band (black circle) + 1 anti-tangle buckle + 1 trainer base, suitable for single training and practice, automatic rebound notes: The actual color of the item may vary slightly from the image on the webpage due to monitor brightness, lighting, and many other factors. Due to manual measurement, please allow 2-3cm size difference.