Abstract: In accordance with the invention a frustoconically shaped stopper formed of silicone rubber approved by the FDA for use in wine making (such as methylvinylpolysiloxane elastomers) can be releasably sealed to a wine barrel, but still provide for sampling of the wine and/or release of the fermentation gases. In this way, all equipment needed for venting, heating and tasting wine can be placed and used in a convenient arrangement with minimum expenditure of time and effort. In one aspect, the stopper of the invention includes a central opening attended by an integral pliant plug having a shaft of length L.sub.0. The central opening is defined by a circular cross section and a length L (measured between an annular base and a truncated tip surface) where L.sub.0 is less than L. A side wall of thickness T is defined. The thickness T varies as a function of the length along the central opening. The side wall is rigid, however.