The ornamental design for flexible tubing, as shown and described.
FIG. 1 is an isometric view of flexible tubing showing my new design;
FIG. 2 is a front elevational view thereof, the rear and side views being mirror images thereof;
FIG. 3 is a top view thereof; and,
FIG. 4 is a sectional view thereof, taken along the line 4-4 of FIG. 2.
The hose is shown with a symbolic break in its length. The appearance of any portion of the hose between the break lines forms no part of the claimed design.