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 court
The ITF's Play and Stay campaign promotes playing on smaller courts with slower red, orange and green balls for younger children. This gives children more time and control so they can serve, rally, and score from the first lesson on courts that are sized to fit their bodies. The ITF has mandated that official competition for children under 10 years of age should be played on "Orange" courts long by wide. Competition for children under 8 years is played on "Red" courts that are long and wide. The net is always 0.8 m high in the center.