Tapered Bung with Airlock & Blow-Off Tube Recess (10mm Bore) A versatile fermentation bung designed to give you flexible options during active fermentation. The tapered design fits a wide range of demijohn sizes, while the 10 mm bored hole is ideal for standard airlocks to keep oxygen out while allowing CO₂ to escape. At the wider end of the bung, a 15mm recessed cavity allows 15mm OD blow-off tube (such as our 12.5mm ID Vinyl Tubing) to seat securely. This makes it easy to switch from a standard airlock to a blow-off setup during vigorous fermentations, helping prevent messy blowouts while maintaining a sealed system. The tapered profile ensures a snug, reliable seal across most common smaller demijohns. It will also fit the Handcraft Supplies 5L Wide Mouth Demijohns. The bung material also adheres better to glass than a standard silicone that can become slippery and pop out. Suitable for Demijohn Sizes: 5L with Flip top Dimensions: Height: 38mm Bore Diameter: 10mm Diameter (Large Taper): 37mm Diameter (Small Taper): 30mm