Stiff Tennis String Wrap the CX around the Multi Core to dramatically increase durability. 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. The MULTI CX 16 (1.30 mm) features a firm hitting feel in the mulch, and it can be used to create a more solid hitting experience for users who have used multiple models. The common mono multi-filament string is good to ride the ball, but you have to carry it with your own force, but the MULTI CX 16 has a comfortable bounce after the ball is rided. Model Number: TS6612NA Material: High elastic special nylon multi-filament, high temperature thread (CX), hybrid high-performance resin, special composite thread gauge, 1.24 mm (17GA). Length: 240m (787FT.) Suitable tension, 45 - 60lbs Color: Natural Country of Manufacture: Japan