Foam Stopper 46-60mm
Breathable foam stoppers will withstand boiling or autoclaving temperatures, making them ideal for use in preparing a yeast starter. The honeycomb structure of the foam stoppers will act as a filter for any airborne bacteria or wild yeast that might enter the flask. That's important because a lot of air is sucked into the flask while it is cooling. You can also leave the stoppers on the flask instead of a fermentation lock. Some people use foam stoppers to replace fermentation locks in their carboys, too.
The large foam stoppers are 46-60 mm wide and fit our 2000 and 5000 ml borosilicate glass flasks.
Actual O.D. is 63mm or 2-1/2". Gotta reach 50 characters for review...that enough?
Great for yeast starters. No longer have to worry about bugs getting into my flask, or having to use the airlock with cotton balls in the top.
Maybe it's due to it being a new stopper and the foam is still rigid and has only somewhat softened up yet after a few uses. It worked it's way out of my 3L flask overnight the first time I used it which let a fruit fly in. The last couple of times I've used it I've covered the foam stopper with tinfoil and wrapped an elastic around it almost defeating the purpose.
It's Foam. It stops.
Well, I checked the box. Found missing one of the stopper. Everything else are very well packed.