The ornamental design for a inner tubeinsert, as shown and described.
FIG. 1 is a top perspective view of the inner tube insert showing my new
design, the broken lines are for illustrative purposes only and form no
part of the claimed design;
FIG. 2 is a side elevational view thereof, the opposite side view being a
mirror image of that shown; and,
FIG. 3 is a top plan view thereof, the bottom view being the same except
that there are no handles.