Gamma Synthetic Gut WearGuard 15L 660' Reel The Gamma Synthetic Gut 15L 660' Reel Wearguard tennis string offers longer life and enhanced playability for all playing levels and styles. The super resilient Dynalon Center Core delivers increased power, while WearGuard Wear Resistant Fibers provide a longer string life with a crisp feel. Ideal for all-court matches. Boasts the perfect blend of feel and durability. Delivers excellent tension maintenance.