The ornamental design for a stackingkit, as shown and described.
FIG. 1 is a front perspective view of a stacking kit, showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is a rear perspective view thereof; and,
FIG. 9 is another front view thereof in a washing machine and dryer environment.
The broken lines illustrating portions of the stacking kit form no part of the claimed design. The broken lines illustrating the washing machine and dryer in FIG. 9 are for environment purposes only and form no part of the claimed design.