Properly designed tennis trainer: it can provide stable support for training because the base has a valve for introducing sand or water to add weight, and the small ring on the side for hanging the tape that concave part for placing the tennis ball, convenient and practical to use. High Stretch String: The elastic cord is highly elastic and wearable. To shorten the rebound, wrap part of the string around the base the length you want. Or you could stretch it for balls hit hard. Super easy to use: Convenient for training without playing ball. You don't need a ball machine or a wall. You can also improve your concentration, your athletic abilities and your hand and eye coordination and develop sports interests. High quality materials: durable and useful PE plastic. It is light and can be taken anywhere you want to practice when empty. The ball can also be used as a pet ball or massage ball. Item package: 1xPower Base, 3xExtra Elastic Strings, 3xTennis Ball. If you have any questions, we will do our best to solve them for you. Product s Tennis trainer for beginners -The perfect portable tennis training aid. Just hit the ball and it will come back to you! -Fill the bottom with water or sand and it will instantly become heavy enough to hold the device in place. Non-slip pads underneath keep it stable. -Unwind the string, hit the ball as hard as you like, and the ball will bounce back towards you. The harder you hit, the faster the ball will be thrown back at you. Specification: Material: woolen cloth + plastic + rubber String length: 3.8m / 150ft Base diameter: 20cm / 7.8in Base diameter: 20cm / 7.8in Color: Blue Scope of delivery: 1 x trainer base 3 x training balls 3 x ropes Steps: 1. Fill the tennis base with water or sand. 2. Tie the tennis ball to the base. 3. Hit the ball slightly upwards to prevent the ball from being pulled back to the ground by the rope.