Wilson NXT 17 Black tennis string is an optimal playing string that provides superior shock absorption and gut-like playability. If you're looking for a premier playability string, then stop here. It also provides comfort and feel. This string is constructed with polyurethane, the same material used for cushioning in your shoes, making it a great choice if you suffer from arm pain. Closest playing string to natural gut. No.1 rated synthetic gut string for playability and comfort (USRSA). Expands sweetspot by 10% and reduces vibration up to 74% compared to traditional synthetic gut. Patented construction using Dupont Xycromicrofibers.