Tecnifibre NRG2 17g (1.24) Black Tennis String - 40 foot pack Gauge: 17 (1.24mm) Length: 40 feet (12.2m) Composition: Multifilament Construction (100% Elastyl Fibers). Features: SPL - Silicon Pyrogene Lubritec additive, which reduces elongation and improves durability by up to 40% Color: Black