This shape is great for beer bottle tops, bottled water tops, poker chips, and envelope seals. It also works well for other small applications such as an accent label (adding a date on canning jars, or indicating different flavors, etc), also as the main label on very small jars and boxes.
The illustration below is not at actual size, but it shows you how this item compares in size to a credit card.
If you are not sure this size will fit your container, draw the shape on a piece of
paper using a ruler to measure, cut it out and lay it on your container.