4 Packs tennis training ball with string tennis trainer balls self practice trainer tool tennis ball training equipment for tennis trainer practice exercise Features: Practical and portable: The tennis training balls with string are suitable for both professional training and daily exercise use, not need to pick up balls, which brings much convenience and makes you enjoy sport time by yourself. You can share them with your friends and family members and do sports together. Easy to use: You can easily tie one end of string to the tennis training ball and fix the other end on racket or ground, then you can start your tennis training, which is convenient and suitable for different places, such as home, yard, park, gym and more. Specification: Color: as pictures shown Ball diameter: 64.2 mm/ 2.53 inches Package included: 4 x Tennis training ball with string Note: Please keep the strings way from little kids to avoid winding risk. Please allow slight size error due to manual measurement.