Head FXP 16g Tennis String Thanks to its special Tri-Cluster FiberGel, this multifilament FXP string provides maximum feel, often referred to as ball pocket feel, to tournament and club players. The secret lies in the tri-cluster fibergel elements and its three so-called gel islands in the string's cross section. In FXP's case, this fibergel is integrated in the core of the string, which results in a softer feel and overall enhanced touch and comfort Length: 40 ft (12 m)