Abstract: A device for sealing a container intended to be connected to a recipient provided with a connector for supply of its contents to the recipient in such a way that the container can be applied to and removed from the recipient without leakage and is sealed after the removal. For this purpose an elastic body is included in the device, which contains a cavity with a thin bottom, which cavity is adapted to the connector and is inclined relative to the longitudinal axis of the body, so that the interior portion of the body is displaced radially time of application of the device to the connector and opens a channel between the body and the container wall for air supply to the container. The interior portion of the cavity is smaller than the exterior portion of the connector to enable the connector to open the sealing device by widening a normally closed hole or slit located at the bottom of the cavity.