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.
TransTrem
The TransTrem (or TT for short) requires custom double ball end strings to work properly. Each string is calibrated to a specific length: as little as 1/16" deviation from this specification adversely affects string tuning. As of 2009 D'Addario, La Bella, GHS and the Steinberger brand strings are the only ones offering calibrated double ball sets.