1. The inner layer is made of high-quality rubber, ensuring the ball's elasticity, stability, and durability. The outer layer is made of high-quality chemical fiber, greatly improving the wear resistance of the ball surface. It is already registered with the trademark AICHUANG. Any additional sales without authorization will result in complaints. 2. Use a rubber band to tie the ball to the base. Hit the ball against the wall with a tennis racket or your hand, or throw it from a distance. Utilize the excellent elasticity of the rubber and the grip of the rope to help the tennis ball return to your hand, eliminating the need to pick up the ball frequently. The ball has a diameter of 6.5 - 6.8 cm (2.56 - 2.68 inches), and the rope is 3.8 meters (12.47 feet) long. The rope - attached tennis ball is an excellent tennis training accessory for developing various tennis skills. You can apply all your tennis skills during training. 3. Application: This trainer is a great training tool for both beginners and advanced tennis players. It is a safe tennis game, highly suitable for both indoor and outdoor sports. 4. Purpose: The straight - line tennis is a tennis training accessory that can help you better develop your personal tennis skills. At the same time, you can throw one to your pet so that your pet can train with you in a fun way. Of course, when the training is over, you can also use it for a comfortable foot and waist massage to relieve fatigue. 5. Specifications: - Material: Rubber + felt - Color: Green - Ball diameter: Approximately 64 mm / 2.5 inches - Length: Approximately 4 meters (When dropped from a height of 2.54 meters, the ball bounces up to 130 cm) 6. Features: - The ball is made of high - quality rubber and felt, lightweight, durable, and easy to carry. By tying the rubber ball to the base, you don't have to waste time picking up the ball, making training easier. - It can improve reaction speed and hand - eye coordination. It is very suitable for tennis learners and tennis training practice, and is highly suitable for both indoor and outdoor use.