The 4S string is the one that will generate the most spin in this range with a square construction that allows even more spin. Tecnifibre is the leading brand in strings and offers a wide range of strings dedicated to all levels and requirements of players. This string has been designed : For the very good and demanding player looking for spin and effect For rackets over 300g For the heavy string breaker ?Colour: black Main material: Co-polyester Recommended tension between 22 and 25 kg Maximum tension: 32 kgs Recommended for heavy string breakers (>10 hours of play). String made in France. Thermocore: Guarantees the greatest flexibility for polyester monofilaments to generate less fatigue. Co-Polyester compound: Selection of polyester granules known for their specific flexibility. High quality material thanks to a mix of different polyesters. Section: Square for maximum effect BEST SELLER FOR LIFTERS A real plus with the square structure. GAME RETURNS The most extreme answer given for lifters by Tecnifibre. Flexible like the Black Code.