[uisgue]

I like this idea, but are they hard to keep clean and sanitized?  I'm envisioning all sorts of crud getting gunked up in the flaps.  Maybe they disassemble for cleaning?  Does anybody have experience with them?

http://www.williamsbrewing.com/10-VENTED-SILICONE-STOPPER-P2667C94.aspx

[pyrite]

Unless you carry out a second fermentation in the barrel I don't think you'll have any problems with the breathable stoppers, I haven't. 
http://www.homebrewersassociation.org/forum/index.php?topic=4652.msg54071#msg54071

[tschmidlin]

What pyrite said.  I use them for extended aging because then I don't have to worry about airlocks drying out, so nothing gets up in there anyway.  But they do come apart if you need to clean them, at least the ones I have.  Those look a little different.  These are what I have.

http://morebeer.com/view_product/16646//Silicone_Stopper_Breathable_-_Carboy

[jaybeerman]

I like them too. Like Tom said, just for extended aging not for active fermentation.

[uisgue]

Are they intended for barrels?  I was thinking that they would go in the carboy after the blow-off tube was removed.

[jaybeerman]

Are they intended for barrels?  I was thinking that they would go in the carboy after the blow-off tube was removed.

they'll work in a carboy