FIG. 1 is a perspective view of a pen cap;

FIG. 2 is a left side elevational view of the pen cap of FIG. 1;

FIG. 3 is a front elevational view of the pen cap of FIG. 1;

FIG. 4 is a rear elevational view of the pen cap of FIG. 1;

FIG. 5 is a top plan view of the pen cap of FIG. 1; and,

FIG. 6 is a bottom plan view of the pen cap of FIG. 1;

The right side elevational view of the pen cap shown in FIG. 1 is a opposite from and a mirror image of the left side elevational view of FIG. 2. The broken lines representing the pen body of FIGS. 1 through 4 are for illustrative purposes and form no part of the claimed design.