The ornamental design for a hairextension, as shown and described.
FIG. 1 is a perspective view of a hair extension, showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a right-side elevation view thereof;
FIG. 5 is a left-side elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view of the hair extension, shown in use.
The evenly sized dash-dash broken lines depicts environmental subject matter that forms no part of the claimed design, while the remaining unevenly sized dash-dot-dash broken lines shown in the drawings depict bounds of the hair extension and form no part of the claimed design.
The use of stippling indicates the ends of the hair follicles.