Bung 25mm - 38mm Silicone Bored (Fits glass demi 5L and 23L)
Silicone Bored Bung 25mm–38mm — Fits 5L & 23L Glass Demijohns
A properly sealing bung is one of those small things that makes a real difference during fermentation and bulk storage. This food-grade silicone bung is pre-bored to accept a standard airlock, fits both the 5L and 23L glass demijohn sizes, and delivers an airtight seal that won't shrink, crack, or taint your wine or cider over time.
Replace your old rubber or cork bung and stop second-guessing the seal.
Why Silicone Over Rubber or Cork
Rubber bungs harden and shrink with age, losing their seal — often at exactly the wrong moment. Cork can taint sensitive wines and is harder to keep clean. Silicone stays flexible and inert indefinitely, holds its shape under pressure and temperature variation, and won't impart any flavour or odour to your batch. It's also easy to sanitise, resisting the chemical cleaners commonly used in winemaking without degrading.
- Food-grade silicone — inert, flavour-neutral, and long-lasting
- Pre-bored centre hole accepts a standard airlock stem
- Tapered profile 25mm to 38mm — fits both 5L and 23L glass demijohns
- Flexible enough to seat firmly without cracking the demijohn neck
- Easy to clean and sanitise between batches
- Reusable — built to last across many fermentations
Compatible Vessels
This bung is specifically sized for the standard glass demijohn neck dimensions used in the 5L and 23L sizes available from The Brew Shop. If you're unsure whether it will fit your vessel, check the internal neck diameter — this bung seats correctly in necks between 25mm and 38mm.
It is not suitable for PET plastic fermenters or carboys with significantly different neck profiles.
How to Use
Push the bung firmly into the neck of your sanitised demijohn until it seats securely. Insert a sanitised airlock into the pre-bored hole and fill the airlock to the fill line with water or Star San solution. The airlock allows CO₂ produced during fermentation to escape while preventing outside air and contaminants from entering the vessel. Replace or check the airlock liquid periodically during long bulk storage periods.
Good to Know
This bung is bored — it has a centre hole for an airlock. If you need a solid (unbored) bung for complete sealing during storage or transport without an airlock, check our solid bung options.