Heavy duty string for high level of comfort Adopts new M7 (monofilament x 7) structure. All-around string that ensures a soft hitting feel and power while providing the most durable Babolat multi-filament. Polyamide String Features: While many racquets are currently hard and powerful, it tends to be difficult to control and feel stiff. The soft polyamide string has excellent hold of the ball for better control and spin, and is comfortable to hit and reduces strain on your arms. The structure is like a bundle of ultra-fine nylon fibers. It has similar properties to natural strings, excellent tension retention and a soft hitting feeling.