Drinking flask

[0001]FIG. 1 is a perspective view of a drinking flask showing my new design;

[0002]FIG. 2 is a front view thereof;

[0003]FIG. 3 is a rear view thereof;

[0004]FIG. 4 is a left side view thereof;

[0005]FIG. 5 is a right side view thereof;

[0006]FIG. 6 is a top view thereof; and,

[0007]FIG. 7 is a bottom view thereof.

[0008]The portions of the drinking flask shown in broken lines form no part of the claimed design.