FIG. 1 is a perspective view of a pen cap, showing the new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right-side elevational view thereof, the left-side elevational view being a mirror image thereof;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken lines showing a pen in FIG. 1, and the opening in FIG. 5 are included for the purpose of illustrating portions that form no part of the claimed design.