Digital 3-Axes Add-OnFeatures Memory of target coordinates Zeroing function at reference point 10 micron digital scale Digital 3 Axes Add On Digital Manipulator Arm, 3 Axes, Add On. The Add On is essentially a complete digital arm that a customer adds on to their existing frame. The digital (add on) arm replaces the customers existing arm. Options Order code Description 505356 Digital Manipulator Arm, 3 Axes, Add On, Left handed 505359 Digital Manipulator Arm, 3 Axes, Add