Tecnifibre X-ONE BIPHASE 16g/1.30mm Tennis String Set is the #1 multifilament string on the market. Its wonderful soft feel is as close to gut as you will get without going to the reel thing. Tecnifibre's BIPHASE process extends the life of the string by 20%. The polyurethane in the string increases elasticity by up to 400% which is what really help in generating power and the soft feel the X-ONE is know for. This string is ideal for racquets under 300 grams to the amount of power it helps to create. It would also make a good hybrid in the crosses with a polyester string.