Li-Ning SS 21 is a Super Series racquet with Dynamic Optimum Frame,Aerotec-Beam System with a High Tensile Slim Shaft . Dynamic-Optimum Frame All-round optimized deisgn improves racquet mechanical structure for more efficient attack and defense system.The sweet point extends upward and the hitting point is moved higher . The effective defense area is enlarged for severe smash by Dynamic-Optimum Frame.The hitting velocity is improved considerablt with widened stringing area and increased bounce strength. Aerotec-Beam System With support of advanced calculation system, the racquets are made with extreme low air resistance and high intensity to enable the players performace in various shots. High Tensile Slim Shaft The top slim shaft design provides extreme strength and easier free control. The 7.0mm top slim shaft design provides extreme strength and easier free control. Perfect balance with racquet weight and moving inertia and aerodynamics.