The Dunlop Black Widow 1.31mm tennis string set is 12m (39.4ft) & is designed with serious players in mind. The string set has a gauge of 16 (1.31mm) & is inspired by one of the world's deadliest predators to ensure unmatched power & exceptional spin. It features a heptagonal outer profile & is constructed of high tensile, monofilament premium polyester.