Abstract: A one-piece valve for a closed enclosure. The valve is formed in the thickness of at least a part of the wall of the enclosure. The valve comprises an inside cavity communicating with the outside of the enclosure by means of a first hole, and with the inside of the enclosure by means of at least one second hole. The valve element is an integral part of the enclosure and occupies the central part of the cavity of the enclosure. The valve can be used for closing inflatable enclosures, particularly balloons, which can be inflated or deflated at will by the user.