While these sleeves do add decoration to the wine bottle, they also have a couple of other practical functions. They help eliminate the growth of mold and bacteria on the outward exposed surface of the cork during storage. And, they also help keep the cork in place, should it decide to push out of the bottle. Our Heat Shrink Capsules are made of a thin PVPP plastic that shrinks when exposed to heat. They can be applied to a wine bottle very easily by placing them over the wine bottle's neck and then dipping them into boiling water for a second or two. Heat Shrink Capsules add a very professional look that grabs attention. They come in several different colors so select what looks best!!