Among all Okinawa weapons the bo is the unique not to have direct influences from China, but its style developed in an independent way and became so effective as to be able to face samurai and pirates who infested the surrounding seas. As an example Matsu Higa, an expert in bo art, fought against "head-hunters" of Formosa and against Japanese pirates coming from north without ever losing any battle. The harmless aspect of bo reveals a tricky nature, because the bo in a Master's hands becomes a terrible weapon. It is gripped with both hands to give it more power and precision. The diameter of bo diminishes from centre to extremities and this means a twofold advantage: control and velocity increase while rotating and moreover it's difficult to trap it with chains.