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What Size Rubber Stopper Fits What?

Posted on February 4, 2010 by Ed Kraus There have been 12 comment(s)

One of things that almost every home wine maker uses is a rubber stopper. It's used to attach an airlock to a plastic fermenter or wine carboy. The rubber stopper is tapered in shape, has a whole in it for the airlock, and comes in various sizes.Rubber Stopper For Making Wine

Knowing what size of rubber stopper to purchase can be of some issue. Whether you are using a gallon glass carboy or plastic fermenter makes a difference as to the size you need. I thought it would be nice to go over, "what size rubber stopper fits what", since there are 25 sizes to choose from.

I should start of by saying that any plastic fermenter we offer takes a size 2 rubber stopper. This may not be the case with a plastic fermenter purchased elsewhere. It depends on the size of whole the supplier decides to put into the plastic fermenter.

Glass carboys come in an array of sizes and take a different sized rubber stopper as the size changes. There are 6.5 , 6 , 5 and 3 gallon sizes. The rubber stopper size for each is as follows:

6.5 Gal. Glass Carboys (Size 6.5)
6.0 Gal. Glass Carboys (Size 6.5)
5.0 Gal. Glass Carboys (Size 7.0)
3.0 Gal. Glass Carboys (Size 7.0)

You may need to size a plastic wine carboy as these have become more popular over time. A plastic wine carboy takes a size 10.0 rubber stopper regardless of its size.

Other sizes of rubber stopper you may need to know is are:

Wine Bottle Opening (Size 2.0)
Large-Mouth Gallon Glass Jugs, Quick Quarter Turn Lid (Size 8.0)
Small-Mouth Gallon Glass Jugs, Thread-Down Lid (Size 6.0)

Visit our website. It lists all of these rubber stoppers and more along with their dimensions.
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

This post was posted in Q&A, Wine Making Blog

12 thoughts on “What Size Rubber Stopper Fits What?”

  • John Licata

    Hi!...Just wondering what the size of rubber stopper or cork would be for old 5 gallon bottles that measure 1 1/4 inch at the opening. Thanks

  • Ed Kraus

    John, It should be a size 6-1/2 rubber stopper. This is based on the measurement you provided.

  • Chris

    I purchased a number 8 stopper so I am assuming that I was wrong and it is actually a small have an opening of exactly 1 inch across across. I have an opening of exactly 1 inch across. Is that a number 6 stopper?

  • Customer Service

    Chris, you are correct. The 1 inch opening takes a size #6 rubber stopper. The size #8 is for large-mouth gallon jugs. The large-mouth can be recognized by the fact that they have a quarter-turn, quick-locking lid.

  • Bryan

    What size stopper would fit a regular gallon plastic milk jug?
    I have been drilling a hold in the lid and using silicone to seal an airlock on top, but I would much rather use a rubber stopper.

  • Customer Service
    Customer Service October 2, 2013 at 7:12 am

    Bryan, for most plastic milk jugs it will be a #6 Rubber Stopper, but it can vary on some rare occasions. I would suggest measuring the inside diameter of the opening. If it is 1", the #6 size will work fine.

    #6 Rubber Stopper

  • Trey

    What size stopper would be used on a 64 fl oz Welch's grape juice bottle? It's a fairly large opening so I'm unsure. Thanks!

  • Customer Service
    Customer Service November 14, 2013 at 6:36 am

    Trey, we have now experience with this bottle. What you will need to do is measure the inside diameter of the opening. Then use that measurement to compare with stopper measurements. You can find all the measurements of our stoppers at the following link:

  • Ed

    I am looking for a cork or stopper for a big mouth jar about 6 1/2" wide. Which size do you recommend?

  • Customer Service
    Customer Service March 15, 2014 at 8:15 am

    Ed, we do not have any size cork or rubber stopper that large. I'm not sure one is made the big.

  • Julie

    What size rubber stopper fits an antique glass gallon milk jug?

    • Ed Kraus

      Julie, I am sorry we do not know what size stopper will fit your antique gallon glass jug. To find out what size stopper you need, measure the inside diameter of the opening and then choose a stopper with a bottom diameter that is slightly smaller.

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