Item #: Q02
Our Price: $1.59
In Stock, Will Ship On 01/27/2020.


Versatile stopper fits Erlenmeyer Flasks made by Pyrex and others (not ours, but other ones that take a #10 to 10.5 stopper). Use as an airlock for yeast culturing, and even more useful as a sterile shield when preparing media. The proprietary foam is heat-resistant, and will withstand autoclaving or pressure cooking, making it an ideal flask plug when preparing sterile wort and agar.

The honeycomb structure of the foam lets the plugged flask breathe, yet bacteria and wild yeast are filtered out and cannot reach the media. This means you can put your media in an Erlenmeyer flask, plug with a Foam Stopper, and pressure cook to sterilize, fully confident that bacteria and wild yeast will not enter the flask, even during the cooling and later storage period outside the pressure cooker.

Works great in our 5000ml flask


Average Rating:
(based on 5 reviews)

Showing 5 Reviews:

Review and Rate this Item
by Jason Gray
on 1/12/2016
from Fresno, CA
Excellent Product
I have used this product for several years now. This stopper does a great job for all of my yeast starters on a stir-plate. I sterilize with Iodophor before using it with my 5000 ml flask.  All positive with no negatives. 5 stars.
by Matt
on 4/10/2014
from Astoria
Use these for Mason Jar Starters
I've been using these for a couple years now on my yeast starters for proper air exchange while thus keeping bad stuff out....essentially acting as a filter.
I use these on narrow mouth Mason Jars that I have pressure canned with wort. I've had no problems using mason jars with stir bars on a plate with this Foam Plug!
by Brise
on 8/18/2012
from Santa Cruz
I have a 2000 ml flask that takes a #10 stopper perfectly. I got his foam stopper and it is too big. Any way I try to insert it into the mouth of the flask makes it all wrinkled up and does not create a good seal. 
by Nicholas
on 4/28/2009
These things are great
Pros: works great for yeast culturing and as an airlock. 

Cons: none that I've found so far.
by Steve S.
on 9/7/2007
Awesome for ehrlenmeyer flasks
Pros: Allows air to go either way and be filtered. I washed it in Iodophor the day before use and let it dry. 

Cons: Retains water fairly easily. Can melt at high temperature.
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1/16/2019 3:13:02 PM
What is the diameter of these stoppers?
2 1/2 inches.
3/26/2018 2:21:16 PM
What material is this? E.g. 1.5lb open cell polyurethane foam.
It is 1.45 lb. open cell uniform density foam, that is autoclavable, chemical resistant, and non absorbent.
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