Abstract: The invention relates to a closure unit for a container suited to filling and dispensing a beverage stored under a pressuring gas. The closure unit comprises a bush from which is disposed a tubular element mounting two concentric valves and a siphon tube which extends into the container. The bush is locked into place in the neck of the container by a threaded locking sleeve which sandwiches a deformable ring between it and the bush. The ring and locking sleeve have respective intermeshing saw toothed profiles which allow locking to occur. This prohibits gas flow from the container between the neck and the bush. Upon unlocking, the profile in the ring becomes fractured thereby depressuring the container.