FIG. 1 is a front view of a plaster ring in accordance with the present design;
FIG. 2 is a rear view of the plaster ring shown in FIG. 1;
FIG. 3 is a top view of the plaster ring shown in FIG. 1;
FIG. 4 is a bottom view of the plaster ring shown in FIG. 1;
FIG. 5 is a left side view of the plaster ring shown in FIG. 1;
FIG. 6 is a right side view of the plaster ring shown in FIG. 1;
FIG. 7 is a front view of a second embodiment of a plaster ring in accordance with the present design;
FIG. 8 is a rear view of the plaster ring shown in FIG. 7;
FIG. 9 is a top view of the plaster ring shown in FIG. 7;
FIG. 10 is a bottom view of the plaster ring shown in FIG. 7;
FIG. 11 is a left side view of the plaster ring shown in FIG. 7;
FIG. 12 is a right side view of the plaster ring shown in FIG. 7;
FIG. 13 is a front view of a third embodiment of a plaster ring in accordance with the present design;
FIG. 14 is a rear view of the plaster ring shown in FIG. 13;
FIG. 15 is a top view of the plaster ring shown in FIG. 13;
FIG. 16 is a bottom view of the plaster ring shown in FIG. 13;
FIG. 17 is a left side view of the plaster ring shown in FIG. 13;
FIG. 18 is a right side view of the plaster ring shown in FIG. 13;
FIG. 19 is a front view of a fourth embodiment of a plaster ring in accordance with the present design;
FIG. 20 is a rear view of the plaster ring shown in FIG. 19;
FIG. 21 is a top view of the plaster ring shown in FIG. 19;
FIG. 22 is a bottom view of the plaster ring shown in FIG. 19;
FIG. 23 is a left side view of the plaster ring shown in FIG. 19;
FIG. 24 is a right side view of the plaster ring shown in FIG. 19;
FIG. 25 is a front view of a fifth embodiment of a plaster ring in accordance with the present design;
FIG. 26 is a rear view of the plaster ring shown in FIG. 25;
FIG. 27 is a top view of the plaster ring shown in FIG. 25;
FIG. 28 is a bottom view of the plaster ring shown in FIG. 25;
FIG. 29 is a left side view of the plaster ring shown in FIG. 25; and,
FIG. 30 is a right side view of the plaster ring shown in FIG. 25.
The broken lines shown represent unclaimed subject matter and form no part of the claimed design.