Drilled Rubber Bung Stoppers for Fermentation
Rubber bungs are used when fermenting to completely seal or create an airtight barrier between the airlock and opening of your fermenter.
Depending on your needs you have two options: Solid Rubber stoppers create a complete seal while drilled rubber stoppers have a hole drill into them which fits a standard size airlock or a small blow-off tube.
Drilled rubber stoppers come in assorted sizes and are required to create an airtight seal in most fermentation. Our food-grade drilled stoppers are made of solid rubber with a pre-drilled hole in the center. This hole is sized to fit all standard-sized airlocks and this blow-off tube. The rubber bung is tapered for a better seal and holds the airlock securely in place. The curved lip also stops the bung from accidentally sliding into your fermenter. These stoppers have many uses in fermentation which include beer brewing, cider, and winemaking, just to name a few.
How does the rubber stopper work?
Plug the stopper into the mouth of your carboy or fermenter and then insert the airlock. This will create an airtight seal that prevents oxygen contact during fermentation. The airlock will then let co2 escape while preventing oxygen from going back into your brewing vessel.
What size rubber stopper do I need for my fermenter?
Stoppers come in various sizes and are sized by number but what do these numbers mean? To determine the correct stopper size, measure the diameter of the mouth of your carboy or fermenter, and compare it to the rubber stopper size chart below. This chart will help you quickly determine which stopper you need by most popular brewing equipment and provides a diameter for each stopper style in inches.
Rubber Stopper Size Chart
Rubber Stopper Bung Sizing Chart
Stopper Type Compatible With:
No. 2 Drilled Stopper fits standard beer and wine bottles.
No. 5 Drilled Stopper fits Big Mouth Bubbler® EVO 2 w/screw-on lid (older EVO 2 models) & Little BMB.
No. 6 Stopper Drilled or Solid fits standard 1 Gallon Jugs.
No. 6.5 Stopper Drilled or Solid fit Glass carboys, Big Mouth Bubbler® plastic (5 or 6.5 gallons), or EVO 2 w/ Universal Lid. The ideal fit is the 6-gallon carboy.
No. 7 Drilled Stopper fit 5 Gallon glass carboys
No. 10 Drilled Stopper fits Bubbler® 5 or 6 gallon
Small Universal Stopper – Drilled or Solid Glass Carboys (3, 5, 6, 6.5), Big Mouth Bubbler® Plastic 5 or 6.5-gallon or EVO 2 w/ Universal Lid.
Medium Universal Stopper – Drilled or Solid Bubbler® 5 or 6-gallon.