Black is back with Tecnifibre 4S. Renamed in 2021 from Black Code 4S (same string, new name), Tecnifibre 4S is a square shaped polyester string designed to have maximum spin and 20% more power than Tecnifibre Pro Red Code. Even though this string does come with more power do not think it cannot last as it has proven to be 15% more durable then its counter part Tecnifibre Black Code, while having the same tension maintenance as Razor Code. All in all a vast improvement in the polyester game from Tecnifibre!