The ornamental design for napkin with ring, as shown and described.
FIG. 1 is a top plan view of a napkin with ring showing my new design;
FIG. 2 is a front elevation view thereof, the left side elevation view being a mirror image;
FIG. 3 is a rear elevation view thereof, the right side elevation view being a mirror image;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a perspective view thereof; and,
FIG. 6 is another perspective view thereof, shown in a possible display configuration.
The broken lines of the border stitches immediately adjacent shaded areas represent bounds of the claimed design and environment while all other broken lines are directed to environment and are for illustrative purposes only. The broken lines form no part of the claimed design. The stitches of the ring form part of the claimed design.