Food-grade silicone is always beet than rubber as it does not leave any taint on the wine or spirit.

These bungs are designed to fit  2Lt Glass Flagons  23L glass carboy and the 11L Glass Carboy. It is a tapered bung and the size is a diameter of 25mm at the base and 38mm at the top . This silicone bung comes complete with a hole to fit a standard sized airlock.

Please note this bung is not suited to the 5Lt Glass 5lt with screw cap. The 5lt Bottles are suited to a Silicone Bung 37-45mm