Ideal for big hitters looking for explosive spin and a powerful punch, Babolat RPM Blast 17 330' reel of 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 the latest polyester with spin-enhancing features, including an octagonal cross section that bites the ball. The 17 gauge still offers plenty of durability and provides slightly better feel than thicker gauge strings. 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.