The ornamental design for an arm sling, as shown and described.
FIG. 1 is a front view of an arm sling in a folded configuration, showing my design;
FIG. 2 is a rear view of FIG. 1;
FIG. 3 is a front view of the arm sling in an open configuration;
FIG. 4 is a rear view of FIG. 3;
FIG. 5 is a bottom view of FIG. 3;
FIG. 6 is a left side view of FIG. 3;
FIG. 7 is a right side view of FIG. 3;
FIG. 8 is a top view of FIG. 3; and,
FIG. 9 is a perspective view of the arm sling in a folded cylindrical configuration.
The arm sling is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claim.
The broken lines in the figures are for the purpose of illustrating portions of an arm sling and form no part of the claim.