Exbolt; A brand new badminton string series from Yonex. The first of this new series is the Yonex Exbolt 63, made from a brand new material called Forged Fiber.Best badminton strings for professional players and your sports clubs. A material which allowed a thinner gauged string to be constructed without compromising durability. Exbolt 63 combines durability, thin gauge and quick repulsion all into one.