Coke Can Cover

1. Cover for a can of opened coke (or any other drink), if you can't finish it
2. The image is actually the cover upside down, so that the inside can be seen
3. There is a rim so that the cap will stay there
4. The smaller circle is a plug, which goes into that hole in the can, to ensure your coke (or whatever drink) doesn't splash out...

There isn't a standard shape/size for the holes in drink cans, so the image just shows a random circle