I claim the ornamental design for a hub cap, as shown and described.
FIG. 1 is a perspective view of a hub cap, showing my new design;
FIG. 2 is an exploded perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a left-side elevational view thereof; the right-side elevational view being a mirror image thereof;
FIG. 5 is a rear elevational view thereof; and,
FIG. 6 is a top plan view thereof, the bottom plan view being a mirror image thereof.
The broken lines showing a wheel and a fanciful number 23 indicia in FIG. 1 and a wheel in FIG. 2 depict environmental matter and form no part of the claimed design. The hub cap is shown on an enlarged scale in FIGS. 3-6.