FIG. 1 is a right rear perspective view of an adjustment arm in accordance with our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right-side elevational view thereof, a left-side elevational view thereof being a mirror image;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken line showing of the model railroad truck assembly and coupler in FIG. 1 is for illustrative purposes only and forms no part of the claimed design.