The Universal Stopper with Hole fits a 2.8, 3, 5, 6, or 6.5 gallon glass carboy. Also fits our 500ml Erlenmeyer flask, and can be flipped over and used in most bottles! Made with a longer taper from a different material from standard stoppers to minimize popping out when wet.
Please Note: This stopper will not fit in plastic carboys, Better Bottles or Speidel Plastic Fermenters.
A good stopper. fits in 64oz and 128oz store bought cider jugs. Felt a little unsure about the seal after multiple times of putting in the airlock. Poured a little sanitizer into the top and no bubbles so I feel that it will seal after multiple reseatings of the airlock. Seems to be a harder material that will withstand the oxidative stress of sanitizer unlike other stoppers and caps that dry and crack.
I have several 5 gallon glass carboys and these stoppers have worked perfectly in them every time. However, I've had a lot of trouble using them with a 6 gallon glass carboy, as the neck is narrower and the stopper hates to slide down and stay in place (wet or dry). 'Sokay, I never liked using that carboy much anyway, and mostly now only use plastic bucket primary and 5 gallon glass secondary. This is a great stopper in my world!
I like these stoppers. As others have pointed out, they need to be dry to fit well, but otherwise, they are much better than the traditional stoppers that behave much worse in terms of staying in the carboy. Unless you go with a carboy cap, these are the stoppers to use.
I like the "universal-ness" of this product. However, when I first do a batch and the neck of the carboy is still wet from sanitizer, these have a tendency to push out and just barely rests on the top of the carboy. I have to use a rubber band to secure it in the beginning.
I almost exclusively use these over the traditional stoppers. These fit a larger variety of sizes and won't get stuck or accidentally pushed through into your carboy. I only wish they made a smaller size that would work with a 6 or 6-1/2 bung hole.