Tecnifibre X-1 Biphase Tennis String Tecnifibre X-One Biphase 16 Rouge is the ultimate in synthetic strings providing the closest playability to natural gut of any synthetic string produced, giving players maximum power, feel, and comfort. Elastyl Fibers are used, giving 12% more power than the standard polyamide materials used in other synthetic strings... X-One Biphase 16G Tennis String Red Size - (See Description)_____Color - (Red) Authorized Tecnifibre Dealer. All racquets are strung and ready for the courts! SEE SELLER DETAILS FOR RETURN POLICY.