Isometric:the square-shaped isometric frame shape is designed to keep vertical strings at a similar length, as well as the horizontal strings to produce an expanded sweet spot in all directions. rotational generator system: by applying the counterbalance theory, weight is distributed throughout the grip end, frame top and the joint for maximum control. the transition to the next shot can be performed smoothly, with rapid succession. solid feel core: the built-in solid feel core cuts harmful miscellaneous vibration at impact. solid feel core is carried in all racquets manufactured in japan. super slim shaft: the slimmest racquet ever produced by yonex vastly reduces air resistance whilst providing maximum feel.