Transpeed something heavy in the trainer's baseboard to make it hard enough to hold the ballDo not need a tennis partner, you can always have tennis training.Especially to improve the tennis player stroke, legwork and hitting precision control.Tie the ball to the base with a rubber band without having to pick up the balls frequently.Pull out the plug of the base, fill the well with water or sand to keep the base stable on the ground.Save yourself from restricting the site, play or practice any place at willFit for white collars, old people, teens, school, entertainment places, etc.Specification:Material: Woolen/ RubberColour blueString elastic ,Package included: 1 set tennis trainning aidNote:The actual color of the item may be slightly different from the images on the web page caused by many factors such as the brightness of the monitor and light.Please allow 2-3cm size difference due to manual measurement.