Enjoy the beer that you deserve.
What it does :
Bungs are useful for sealing the openings in fermentation vessels. They also provide an installation fitting for an airlock, whether in a plastic bucket lid or a glass carboy opening.
What it is:
A bung is a stopper, typically made of rubber, used to seal holes.
How it works:
Bungs are simply good for plugging carboy and bucket openings, nothing more and nothing less.
Bungs are used during the cold side of brewing (e.g. fermentation, bottling, and packaging). They are directly exposed to the beer during the critical fermentation stage. So, spigots should be sanitized before use to prevent contamination.