1 2 3 4 H H H H * v X v * v X * v * handedness 1 2 3 L handedness 1 2 4 L handedness 1 3 4 L handedness 2 3 4 R length 1 H 8 100 length 2 H 8 100 length 3 H 8 100 length 4 H 8 100