NEW CRYSTAL: New fibre for the core of the Corelli CRYSTAL strings, new computer-based technology and even more accurate automated tests during production have further enhanced the characteristics of the popular CRYSTAL strings ;Larger overtones, fast and more accurate response;quality sound projection from pianissimo to fortissimo;C Nylon/Tungsten wound;Tension Light 6.3kg / 13.9lbs;Medium 6.6kg / 14.6lbs;Strong 6.9g / 15.2lbs;