Tecnifibre X-One Biphase Tennis String Set in Natural is the ultimate synthetic string and provides the closest playability to natural gut of any synthetic string produced. Elastyl Fibers are used, giving 12% more power than the standard polyamide materials used in other synthetic strings. X-One Biphase features a unique technology that separates it from other strings in the Tecnifibre line, Fiber H2C, which involves a high temperature prestretching step to ensure greater tension maintenance. Improving on their PU Inside technology, this string features Trimerized PU, allowing for even more comfort and touch for that natural gut like feel. Many years of research have led to the Biphase process, a production process that increases string durability by 20%, letting players experience the benefits of this string for even longer. The most advanced synthetic string on the market, X-One Biphase makes the playability of natural gut available in a synthetic alternative. X-One Biphase gives players more power, comfort and feel.