Muscle Power is Yonex’s futuristic design of rounding corners to help realize the frame’s full power potential. Instead of seating the string on the sharp points of a traditional grommet hole system, Muscle Power seats the string on Round Archways that cause no string stress-load and no fatigue through contact friction. The construction creates total unity of the frame and string because they are in much closer and tighter contact. The face stability that results from rounding the corners lets you smash with a new magnitude of aggression.