X-One Biphase is Tecnifibre's premium string. It is designed to take playability and durability to a new level by providing ultimate performance of power and feel, while extending string life by 20% and offering increased spin. X-one Biphase joins together H2C (High Heat Capacity) and NRG microfilaments to acquire this high power and dynamic response. X-One benefits from a process (trimerization), which bonds polyurethane to protect against wear and notching while maintaining high comfort and feel.