Teloon springen Tennis Trainer Rebound Ball Iron Base Tennis Training Tool，2.35LB Weight Heavy with 2PCS Replaceable String Self-Study Rebound Ball Baseboard Sparring Device（Black）

Only used it twice because The string broke off from the ball. Other than that it's good for foot timing

I wanted to really like this product. In theory, it's a great product for small spaces, backyards, driveways, but the built quality was so subpar. Both the ball and string that came attached to the base unit and the extra ball and string broke after a couple of uses and the string tends to bunch up so if I wasn't taking a full swing, the ball might not actually make it back to where I was.