Product Description Color: Natural X-One Biphase is Tecnifibre's latest 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 produces a lively firm feel, produces tremendous control, and holds tension well. Composition: Composite Microfilament, Biphase process and immersed polyurethane. Gauge: 16g (1.30mm), 17g (1.24mm), 18g (1.18 mm) Length: 39' Durability: 16g= 7.8, 17g= 6.5 Playability: 16g= 8.9, 17g= 8.8 Misc.: Tecnifibre recommends pre-stretching this string.