FIG. 1 is a front view of the right in-ear headphone;

FIG. 2 is a back view of the right in-ear headphone;

FIG. 3 is a left side view of the right in-ear headphone;

FIG. 4 is a right side view of the right in-ear headphone;

FIG. 5 is a top plan view of the right in-ear headphone;

FIG. 6 is a bottom plan view of the right in-ear headphone;

FIG. 7 is a front view of the left in-ear headphone;

FIG. 8 is a back view of the left in-ear headphone;

FIG. 9 is a left side view of the left in-ear headphone;

FIG. 10 is a right side view of the left in-ear headphone;

FIG. 11 is a top plan view of the left in-ear headphone; and,

FIG. 12 is a bottom plan view of the left in-ear headphone.

The broken lines form no part of the claimed design.