(Click to see larger image) Narishige's SM-15M-2 sub stage adds Y-axis movement to the SM-15. The standard SM-15 has X- and Z-axis movement units, but no Y-axis movement (i.e. the same direction as the AP frame bar). This one-axis fine movement unit can therefore be placed between the AP frame bar attachment point and the SM-15 body. This enables smoother, more precise adjustment than was possible by the former method of adjusting the Y-axis with the sliding AP frame bar.

Compared to the SM-15M, this sub stage moves forward when the control knob is rotated clockwise instead of counterclockwise. Scales and pointing lines are placed on both sides of the body instead of just one side.