A premium multifilament string, X-One BiPhase delivers superb comfort, feel and a crisp response. A good choice for players seeking an arm-friendly string without sacrificing power. Provides good tension maintenance too. According to Tecnifibre, the X-One Biphase string uses High Heat Capacity (H2C) fibers, which allows the use of an innovative chemical treatment process called Trimerization. This new process increases the cohesion between chemical molecule links through extreme variations in temperature to result in ultimate dynamic efficiency (power) and exceptional feel. The new patented Biphasic process, with its visible marks on the string, extends string life by 20% and offers increased spin. Similar to its leading string, NRG2, the multifilament fibers within this string are immersed in polyurethane to provide shock absorption and optimum comfort.