The ornamental design for a pair of boot soles, as shown and described.
FIG. 1 is a perspective view of a left-foot boot sole of a pair of boot soles embodying my new design;
FIG. 2 is a bottom view of the left-foot boot sole of FIG. 1;
FIG. 3 is an enlarged bottom view of a front portion of the left-foot boot sole of FIG. 1; and,
FIG. 4 is an enlarged bottom view of a rear portion of the left-foot boot sole of FIG. 1.
The boot sole design shown in FIGS. 1-4 depicts a left-foot boot sole of my new pair of boot soles design, and a right-foot boot sole is a mirror image of that shown in FIGS. 1-4.