There alsome there work great

Excellent product. Super useful for yeast starters in flasks on stir plates.

This is has made foil obsolete.

As advertised. Very happy

These stoppers are great for yeast starters in an Erlenmeyer flask. Keeps bacteria out while allowing airflow

It fits nicely in my 5 liter flask.

Bought a 10-pack because I'll probably lose or misplace them. Fits my starter flask perfectly.

These stoppers do the job as advertised

Only used once, but perfect fit on 2000 ml starter flask.

I tried this with soy venting sanitized jug and had too watch very careful LOL pay’s to have right stuff. (was out aluminum foil)

Works as advertised.

My starter flask just loves her new foam stopper, so spongy, easy to sanitize, and sooo comfortable. Can’t wait for those little yeasty’s to try to get out as there’re in for a big surprise.

Does the job as the stir plate spins away.

It fit my 2000 ml Erlenmeyer Flask from my local brew supply just fine. The only reason I knocked off a star is because I got a little wort on it when swirling the flask; and that caused it to stick to the inside of the neck. Upon removing it to pitch my starter, I noticed a tiny bit of foam peeled off and was stuck to the glass. I did cold crash and decant the yeast, so it was in my flask for 2 days total. The residue/foam was easy to remove from the flask and I really can't see where any is missing on the stopper itself. So I'd say the durability is still quite good, but I just wished it hadn't peeled off so easily. In the end it's probably my fault, and I wouldn't hesitate to buy again.

Making yeast starters is much simpler when using the foam stoppers. Using aluminum foil works but the stoppers are much more convenient.

Worked as described. Used with yeast starter.

worked well on my flask with propper yeast starter.