The Gamma Zo Verve 1.25mm tennis string set is 12.2m (40ft) long & ensures maximum power & greater spin for deeper shots from anywhere on the court. It is ideal for hard hitters & offers an amazing combination of ultra high molecular weight polyester (black) providing ultimate durability & spin, & the co-extruded Zo high energy co-polyester core (red) for outstanding elasticity, max feel & power. The string set has a gauge of 17 (1.25mm) & features a blend of stiff & soft materials for perfect performance.