Stiff Tennis String Wrap the CX around the Multi Core to dramatically increase durability. Fine-gauge multi-CX16 for increased spin This is a new type of string that is not poly or nylon with a combination of durability and a nylon hold. Uses Aramid series super fiber with excellent heat resistance of CX, and has succeeded in commercial. CX stands for Caloric Xtra Super Heat Resistance. The CX is a fiber that can withstand up to 430 degrees Celsius whereas common nylon and polyester strings melt at 210 to 250 degrees Celsius. The CX fiber is wrapped around the mono multifilament to create an ultra-durable mono multi-filament that is hard to beat the friction between the ball. MULTI CX Fine Gauge Type (1.24mm) Among the multi features a firm hitting sensation, allowing users to feel a more solid sense of hitting when using multiple models. Increased control and easier spin Model Number: TS661 Material: High elastic special nylon multi-filament, high temperature thread (CX), hybrid high-performance resin, special composite thread gauge, 0.05 inch (1.24 mm) (17 GA.) Length: 40 ft (12.2 m) x 20 tensile non-packaging Suitable tensioning 45 - 60 lbs Color: Natural Country of Manufacture: Japan