Abstract: The hermatic seal unit is for a container having a lower portion and an upper portion of a slightly greater diameter. There is a shoulder portion at the junction of the upper and lower end portions. The device includes a cover conforming in shape to the upper portion of the element. Spreader elements are pivotally positioned in the cover. The hermetic seal element is positioned on a lower portion of the cover and the spreaders are in contact with the inner surface of the hermetic seal element. The hermetic seal element is in intermittent contact with the top portion and shoulder of the container in order to intermittently define the hermetic seal.