I claim the ornamental design for an extrusion, as shown and described.
FIG. 1 is an above front perspective view of an extrusion showing my new design;
FIG. 2 is a below rear perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left view thereof;
FIG. 6 is a right view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is an underneath view thereof.
The extrusion is shown with a symbolic break in its length, which break is rendered in dot-dot-dash broken lines. The appearance of any portion of the article between the break lines forms no part of the claimed design. The dot-dot-dash broken lines in the drawings define the bounds of the claim and form no part of the claimed design.