Tennis Ball Machines. Versatile and essential, tennis ball machines are the perfect practice device for coaches and instructors or the serious players who want to take their tennis game to the next level. They allow you to train against many different strokes, with some models able to feed balls in random patterns.What is a tennis ball?
A tennis ball is a ball designed for the sport of tennis. Tennis balls are fluorescent yellow at major sporting events, but in recreational play can be virtually any color. Tennis balls are covered in a fibrous felt which modifies their aerodynamic properties, and each has a white curvilinear oval covering it.