The 2 piece rubber mini keg bung is a reusable bung that is used to seal the mini keg when carbonating your beer. After 2 -3 weeks of carbonation time, your beer should be ready to tap. All you have to do is push the long rod of the party star tap system into the center of the rubber bung, and let the plastic piece fall into the keg. When the keg is done, fish out the plastic center, clean it, attach it to the rest of the bung, and you are ready for the next use.