Ideal for big hitters looking for a powerful punch and explosive spin, Babolat RPM Blast 18 tennis string is a co-polyester string with a fast and powerful response. As used by Rafael Nadal, Jo-Wilfried Tsonga and Samantha Stosur. This string is designed to maximize spin potential and durability. Premier choice for chronic string breakers. The 18 gauge still offers enough durability while providing much greater feel and spin. High density co-polyester construction provides a fast and powerful response with great ball speed out of the frame. An octagonal structure with cross-linked silicone provides maximized spin. Cross-linked silicone coating provides a unique feel.