Kunai is not a standard article and therefore it comes in various sizes and shapes, and its center of gravity is unstable because it was originally made as a tool, not as a throwing weapon, as described above.
規格品ではないためにサイズにも形にもバラつきがあり、元来前述のように投擲武器としてではなく工具として作られたため重心が安定していない。