Rubber Stopper – Bung Stoppers for Fermentation – Home Brew – Beer, Cider, Wine Making


Rubber Stopper For Fermentation

  • Non drilled Solid Rubber Stoppers Available Here
  • It creates an airtight seal, keeping oxygen out
  • Food grade rubber
  • Variation Size for Different Size Requirements #2, #5.5, #6, #6.5, #7, #7.5, #10, #10.5, #11
  • Rubber Stopper Bung Sizing Chart
Select a product variation to get estimate


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.

Rubber stoppers come in assorted sizes and are required to create an airtight seal in most fermentation. Our food-grade stoppers are made of solid rubber. 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. This will create an airtight seal that prevents oxygen contact during fermentation.

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.

Stopper Type Compatible With:

No. 2 Stopper fits standard beer and wine bottles.
No. 5 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 Solid Stopper fit 5 Gallon glass carboys
No. 10 Solid 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.

Our Mission Is Your Success

Fermentaholics is a team dedicated to making your homebrewing and home fermenting experience a success. From the moment you place your order, you gain immediate access to our network of fermentation experts here to help you along your journey. No matter your question or concern, we are here to provide the correct guidance and support to help you accomplish your fermentation goals. From batch to batch and brew to brew, we’ve got your back.

Additional information

Weight .2 lbs
Dimensions 1 × 1 × 1 in
Solid Rubber Stopper

# 2 Solid Rubber Stopper, #5 Solid Rubber Stopper, #5.5 Solid Rubber Stopper, # 6 Solid Rubber Stopper, # 6.5 Solid Rubber Stopper, # 7 Solid Rubber Stopper, # 7.5 Solid Rubber Stopper, # 10 Solid Rubber Stopper, # 10.5 Solid Rubber Stopper, # 11 Solid Rubber Stopper


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