Gamma Synthetic Gut 16 Gold 720 is an all-around performance tennis string that offers a balance of playability and durability for all playing levels and playing styles. The 16/1.30mm gauge string boasts a slightly thinner circumference than the 15L, but still offers plenty of durability. This gauge still offers quite a bit of durability with a bit more power and playability than the 15L. Ideal for hard hitters and chronic string breakers who don't mind restringing a littler more frequently in order to get more power. Solid Core Synthetic string. Combination of Nylon 6 core, nylon monofilament wraps, nylon coating and Gamma Irradiation Processing for exceptional all-around performance and extra playability with superior durability.