Although the name is "tennis trainer", I don't recommend you to practice this. Because of the rubber band, the ball will come back no matter where you hit it. However, a real tennis court has boundaries and nets. You hit high and out of bounds; Lower and lower the net.

So I have been telling others that it is just a fitness equipment made of tennis equipment and has nothing to do with tennis.

If you just want to keep fit, then this is ok. Don't practice tennis if you want to. The more you practice, the worse things will get. Hmm. How interesting