The Wilson NXT Power 17 660' Reel features high                        crystallinity xycro microfibers bonded with polyurethane for an            ideal combination of soft feel and explosive power upon contact.           Rated as the #1 comfort string by USRSA, the NXT Power 17                  features a 15% larger sweet spot and 80% less vibration than               traditional synthetic gut string. The core is composed of a                ribbon-like co-polymer, increasing tensile strength and reducing           the tension lost while hitting shots. Originally labeled NXT               Tour, this string's softness and comfort are about as close as             it comes to natural gut. This 17 gauge string is slightly                  thicker than the 16 gauge, making it a more durable option.