The ornamental design for an earplug, as shown and described.
FIG. 1 is an isometric view of an earplug showing our new design;
FIG. 2 is a side view thereof, the opposite side view being a mirror image;
FIG. 3 is a top view thereof, the bottom view being a mirror image;
FIG. 4 is an end view thereof, as seen from the left of FIG. 2;
FIG. 5 is an end view thereof, as seen from the right of FIG. 2;
FIG. 6 is an isometric view of an ear plug according to the present invention with the connector and second ear plug shown in broken line for environmental purposes only and forms no part of the claim design; and,
FIG. 7 is an isometric view of an ear plug according to the present invention showing the opposite end as that shown in FIG. 1.
The broken line showing in FIGS. 1-5 and 7 are for environmental purposes only and forms no part of the claimed design.