The ornamental design for an under seatstoragebox for vehicles, as shown and described.
FIG. 1 is a perspective view of the under seat storage box, which embodies the present invention;
FIG. 2 is a rear view of the under seat storage box seen in FIG. 1;
FIG. 3 is a front view of the under seat storage box seen in FIG. 1;
FIG. 4 is a right side view of the under seat storage box seen in FIG. 1, the left side view being a mirror image thereof;
FIG. 5 is a top view of the under seat storage box seen in FIG. 1; and,
FIG. 6 is a bottom view of the under seat storage box seen in FIG. 1.
In the drawings, the broken lines depict environmental subject matter only and form no part of the claimed design. Shade lines having a combination of long and short lines in the drawings show contour and not surface ornamentation.