The Wilson NXT 17 tennis string provides excellent feel, comfort & playability ensured by proprietary Xycro Micro Fibres impregnated with PU. The string is 17 (1.24mm) in diameter & has a multifilament construction that makes it a good choice for players suffering from tennis elbow or other arm problems. It is sold as a 12.2m (40ft) long set that enables you to re-string one racket with it.