The ornamental design for a mouthpiece for a blunt, as shown and described.
FIG. 1 is an enlarged top-front-left perspective view of a mouthpiece for a blunt showing my new design;
FIG. 2 is an enlarged bottom-rear-right perspective view thereof;
FIG. 3 is a front elevated view thereof;
FIG. 4 is a rear elevated view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a left elevated view thereof;
FIG. 8 is a right elevated view thereof; and,
FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 8.
The broken lines showing of a mouthpiece for a blunt tip in FIG. 1-9 are included for the purpose of showing environmental structure and form no part of the claimed design.