Best in class for comfort, feel and power, Wilson's Natural Gut is regarded as the premier tennis string despite modern synthetic advancements. Comprised of natural serosa fibers treated in bath of stabilizing chemicals with outer coating applied for protection, this string is incredibly arm-friendly and powerful. New manufacturing techniques have improved its durability by 15% compared to previous versions of the string. This type of string holds its tension better than any other string, so you can be confident that the original tension will remain in the racket for longer periods of time. The 17 gauge string is slightly thinner than the 16 gauge, which enhances feel and control.