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Fermentology Carboy Caps are the perfect accessory for brewing homemade wine, beer, mead, kombucha and more in big glass carboy jugs, including 3, 5 and 6 gallon volumes. The silicone caps stretch to fit over the mouth of the jugs so they can be used with a number of different jug styles universally. Each lid has two tubes that can connect with brewer equipment accessories, like airlocks, siphons, tubing, or racking canes, and also has 2 posts to house white sealing caps so they never go missing when you need them. The white caps can be moved from their hosing stations to cover the opening of the tubes if only one accessory needs to be attached, or to cover both openings to create an airtight seal to replace the use of corks. Each pack includes 4 lids and 8 white caps and is made of top quality silicone that can be washed by hand or in the dishwasher. These Car Boy Airlock Caps are part of the Fermentology suite of products; Fermentology are experts in home fermentation weights, tampers, stoppers and more for wide and regular mouth Mason jars and carry a variety of supplies and kits for fermenting, like waterless airlocks, traditional airlocks.
Airlock-Ready Carboy Caps for Brewing
Each set includes 4 caps that fit over the mouth of carboy jugs to attach fermenting and brewing accessories. Fits 3/5/6 gallon carboy jugs without needing any threading; simply stretches to fit over the mouth of the jug
Never Lose the Caps
Each lid has two housing posts to safely store the caps when not in use, so they’re always there when you need them.
Lids Fit 1 or 2 Accessories
Each lid can be fitted with two fermenting or brewing tools, like airlocks, tubes, siphons, racking canes and more.
Doubles as a Cork
Block off unused pipe openings with sealing caps if only one accessory is needed, or put them both on to create an airtight seal to replace the use of a cork.
Universal Fit for Carboys
The silicone caps have an inner diameter of 49.7mm that can be stretched to fit over the mouth of carboy jugs. The spouts have inner diameters of 9mm and 6mm for inserting brewing equipment into, but can also be stretched to fit larger accessories. Fermentology carboy caps can fit 3, 5 and 6 gallon jugs.
Food Safe, Quality Materials
All Fermentology products are made of food safe and high-quality plastics and silicones. The items included in this box kit are BPA-free and phthalate-free. All of our fermenting equipment is designed in-house by a group of avid fermenters in Toronto, Canada.
Part of a Suite of Fermentation Products
This set is one of many fermentation tools Fermentology has to offer. Our other products include waterless airlocks with pumps, traditional airlocks, fermentation weights, and vegetable tampers. We have equipment for all styles and levels of experience when it comes to lacto fermenting vegetables.
Matt
September 7, 2025
I have a random collection of glass and PET carboys with slightly different opening sizes. These fit most and are easy to setup with an airlock. Silicon makes them stretchy and soft.
Jonathan Hicks
September 4, 2025
I am an early home brewer and bought these so I wouldn't have to mess with fitting bungs. I couldn't get the right size bung, or it would slip out. This product completely fixed that problem and then some! You can fashion one into a blowoff apparatus if you connect tubing to it, and it works great! I threw away all of the other bungs I had and I use this cap EXCLUSIVELY. I will be buying these from now on.
Whitehorse
August 18, 2025
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T. Porter
August 14, 2025
These are a lot easier to install and remove than the traditional rubber or silicone bung and seal just as well. I wish they made one for one gallon jugs.
Kaleidoscope
August 10, 2025
Trying to reduce my daily exposure to plastics, and this was the only silicon cap I found so far. Bonus opening taps help relieve pressure when trying to close over a jug, and also doubles as water taps if jugs are tipped over carefully with a silicon matt or coaster (avoiding having to buy a plastic tap).
Honest Opinion.
July 23, 2025
They seem well made, should last a long time and if they fit my carboys I would have been satisfied! However that was not the case. It's my fault for not breaking out the calipers and measuring the diameter of my bottle opening. I would recommend that you make sure that your carboys are sized to fit these before purchasing. That aside, they're are well made, very functional and I would recommend them without hesitation. Just make sure you use their pictured measurement guide in the product description photos to make sure they fit your carboy. I knocked off 1 star because in the description it states they will fit a 6.5 gallon carboy but they did not fit my Italian made carboy 6.5 gallon. I was able to get them to work using a zip tie. So, not a total loss.
Matt
June 20, 2025
I have a random collection of glass and PET carboys with slightly different opening sizes. These fit most and are easy to setup with an airlock. Silicon makes them stretchy and soft.
Jonathan Hicks
June 17, 2025
I am an early home brewer and bought these so I wouldn't have to mess with fitting bungs. I couldn't get the right size bung, or it would slip out. This product completely fixed that problem and then some! You can fashion one into a blowoff apparatus if you connect tubing to it, and it works great! I threw away all of the other bungs I had and I use this cap EXCLUSIVELY. I will be buying these from now on.
Whitehorse
June 13, 2025
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T. Porter
May 28, 2025
These are a lot easier to install and remove than the traditional rubber or silicone bung and seal just as well. I wish they made one for one gallon jugs.
Kaleidoscope
May 26, 2025
Trying to reduce my daily exposure to plastics, and this was the only silicon cap I found so far. Bonus opening taps help relieve pressure when trying to close over a jug, and also doubles as water taps if jugs are tipped over carefully with a silicon matt or coaster (avoiding having to buy a plastic tap).
Honest Opinion.
May 26, 2025
They seem well made, should last a long time and if they fit my carboys I would have been satisfied! However that was not the case. It's my fault for not breaking out the calipers and measuring the diameter of my bottle opening. I would recommend that you make sure that your carboys are sized to fit these before purchasing. That aside, they're are well made, very functional and I would recommend them without hesitation. Just make sure you use their pictured measurement guide in the product description photos to make sure they fit your carboy. I knocked off 1 star because in the description it states they will fit a 6.5 gallon carboy but they did not fit my Italian made carboy 6.5 gallon. I was able to get them to work using a zip tie. So, not a total loss.
Ana Maria Arias Rivera
May 18, 2025
Excelente producto!
Jeanette Moser
May 6, 2025
These are a good fit on my 5 gallon carboys work better than the ones that came with them, this is my first wine making adventure and I am leaning so much.
Joseph G
May 4, 2025
These silicone carboy caps are excellent, easy to use and provide a tight seal, they stretch and seal around the carboy opening. These caps are a quality product. ​I use them on the 11.5, 19, and 23 liter carboys made in Italy and Mexico , no issues at all. Some wine when it has a little of residual sugar content left may creature pressure and pop caps off the carboys because of the tight fit. In these cases I will then stretch an elastic band around the cap to give it greater holding power.
Edward Tuite
April 17, 2025
Good fit on a 20ltr glas bottle
Manuel Meier
March 26, 2025
Perfect for Carboy jugs.
Thomas Glaesing
March 21, 2025
Bought these and they fit very well on the carboy. Sit in place and don't pop off. I prefer these over any other bung I have. A modern and effective take on cork/hard Silicone bungs.
Integrity2017
March 19, 2025
Product meet expectations
Ana Maria Arias Rivera
February 26, 2025
Excelente producto!
Jeanette Moser
January 15, 2025
These are a good fit on my 5 gallon carboys work better than the ones that came with them, this is my first wine making adventure and I am leaning so much.
Joseph G
December 23, 2024
These silicone carboy caps are excellent, easy to use and provide a tight seal, they stretch and seal around the carboy opening. These caps are a quality product. ​I use them on the 11.5, 19, and 23 liter carboys made in Italy and Mexico , no issues at all. Some wine when it has a little of residual sugar content left may creature pressure and pop caps off the carboys because of the tight fit. In these cases I will then stretch an elastic band around the cap to give it greater holding power.
Edward Tuite
December 9, 2024
Good fit on a 20ltr glas bottle
Manuel Meier
November 26, 2024
Perfect for Carboy jugs.
Thomas Glaesing
November 25, 2024
Bought these and they fit very well on the carboy. Sit in place and don't pop off. I prefer these over any other bung I have. A modern and effective take on cork/hard Silicone bungs.
Integrity2017
November 17, 2024
Product meet expectations
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