Abstract: A closure device has a hollow body with a side opening for liquid, an open end, and a closure end portion, and is slidably engaged in an end-piece screw-threadedly engaged on the end part of a neck of a bottle. The closure device seals the bottle when pressed down into the neck until its closure end portion seals against a ridge defining the end mouth of the outlet conduit constituted by the neck and its end-piece. When the device is raised to engage a lower bead in a groove of the end-piece, liquid can be poured out of the bottle by way of the interior of the hollow body and the opening while air enters the bottle by way of an air inlet region and venting passages leading to an air outlet port. An inner barrier to liquid is formed by contact between the widest part of a skirt of the hollow body and the internal surface of the neck.