Strings (tennis)
In tennis, the strings are the part of a tennis racquet which make contact with the ball. The strings form a woven network inside the head (or "hoop") of the racquet. Strings have been made with a variety of materials and possess varying properties that have been measured, such as dynamic stiffness, tension retention, thickness (gauge), string texture (shape of the string), and rebound efficiency.
Tennis ball
The ITF's "Play and Stay" campaign aims to increase tennis participation worldwide, by improving the way starter players are introduced to the game. The ITF recommends a progression that focuses on a range of slower balls and smaller court sizes to introduce the game effectively to both adults and children. The slowest balls, marked with red, or using half red felt, are oversized and unpressurized, or made from foam rubber. The next, in orange, are unpressurized normal sized balls. The last, with green, are half pressured normal sized.