Rubber stopper with center plug for five-liter mini Party kegs. Grey. Can be reused. UsageWhen you insert the stopper in the keg, push down around the outer edge. If you push down on the center plug, it may fall into the keg. When it's time to start serving beer, push the dip tube of the dispenser through the rubber stopper. The dip tube seals against the rubber stopper and the center plug falls into the keg.