What is it?
A bored cork bung (cork with a pre-drilled hole) that allows an airlock to be fitted to the opening of glass demijohns or some plastic fermenters. This is the standard size to fit glass demijohns. These are too small for plastic demijohns. The image shows the bung at two different views, you will receive only 1 bung. The top of the cork measures 31mm, the bottom 27mm.
Why do you need it?
If you plan on fermenting in glass demijohns then you must have an airlock fitted, as the demijohns do not hold pressure. You need the carbon dioxide that is created during fermentation to escape through an airlock.
How do you use it?
Simply push the cork into the hole for a good seal. Be careful not to push in too hard, as some jars have slightly larger openings and the cork may go in. The airlock will then push into the hole in the bung.
To fit an airlock, there is also a bung made from rubber. To store for long periods, use a solid bung that are available in either cork or rubber.
Tips:It will be easier to fit the airlock into the bung before fitting it in your fermenter.Be careful if using a glass airlock, if you slip pushing the airlock in the hole, it could cause damage to your skin.Soak the cork for 20 minutes before first use, this will help with sealing.