Solo Tennis Trainer Set Single Self-Study Training Device Rebound Ball PracticalFeatures: Add the weight The base comes with the stopper that allows you to place the sand or water inside it to add the weight. Concave part design The small ring aside can help you tie the string, while the concave part can place the tennis ball. Multifunctional and practical This tennis trainer is lightweight, convenient, practical, easy to use, and can provide stable training support, contributing to single player exercises. It can also improve