I claim the ornamental design for a tube, as shown and described.
FIG. 1 is a perspective view of the tube showing my new design;
FIG. 2 is a front view thereof, the rear view being a mirror image thereof;
FIG. 3. is a side view thereof;
FIG. 4. is a top view thereof; and,
FIG. 5. is a bottom view thereof.
Inner horizontal lines at the upper and bottom ends of the tube show the sealed portion of the claimed design.
The shade lines present on the perspective and front views show that the container portion is rounded and protuberant in contrast to the flat sealed portion.