Solid tennis racquet string By further increasing the rigidity of the VOLT (Volt) material, it achieves a firm hit and high speed spin that is preferred by a fast swing speed power hitter. The string "VOLT POWER" is a "hexagonal cross-section". The triangle is easy to snap in the corners, and the pentagram will leave a flat surface, and an octagonal shape will be too round. The hexagonal cross-section shape has been reached after trial and error. It involves the friction effect when spin, providing a variety of play performance.