Composition: composite microfilament biphase process and polyurethane Gauge: 16g (1.30Mm) 17g (1.24Mm). Length: 660'(200m) Durability: 16g- 6.76 17G- 6.3 Playability: 16g- 8.71 17G- 8.6 Misc.: Tecnifibre recommends pre-stretching this string. 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. X-one is the string of choice for roland garros.