Abstract: The disclosure describes a seal bung for the closure of a bottle, comprising a central body, a part for sealing hold against the bottle glass finish internal wall, and an annular flange with bell-shaped edge, suitable for being held in an internal groove of the metal closure and hugging the rim of said glass finish. The seal bung comprises a central hollow body, an inward-looking closed bottom an annular flange extending from the top of the central body circumferential wall, said part being composed by a lip extending from the flange towards the inside of the bottle and separated from said wall so that it forms an annular hollow space communicating with the inside of the bottle.