This Fill & Drill Tennis Self-Training Kit is a portable and convenient tool that helps you practice tennis anytime & anywhere. It is easy to use, just fill in the base with sand / water and start playing right away. There is a nylon rope attaching on the ball, you don't have to pick up the ball from time to time. It is time-saving and more convenient. You can also train your reaction and swinging speed by training with the quick rebounding ball. The non-slip mat holds the training tool firmly on any surface. Let's get it now! Features: Independent Training: With this kit, you can start training independently even if you can't find a partner. The ball is retractable and easy to practice multiple times. Advance Speed Drilling: The ball is rebounded quick & fast, it helps train your reaction and speed of swing. No More Pick & Run: As there is a rope attaching on the ball, you don't have to pick up the ball after the hit. It is more time-saving and convenient. Non-Slip Mat: Just put sand or water into the base, there is a non-slip mat that hold the base firmly on any surface. Multi-players: You can practice by yourself or play with your friends and family.