Single Hole Red Rubber Carboy Cap

[AnOldUR]

They've probably been around, but I've never seen this style carboy cap before. Looks like they stretch over the top of a carboy. Anyone using them? Better or worse at sealing than the standard ones with two stems?

 

[BrewCityBaller]

They've probably been around, but I've never seen this style carboy cap before. Looks like they stretch over the top of a carboy. Anyone using them? Better or worse at sealing than the standard ones with two stems?

I always assumed they plugged into the hole like a bung... Learned something new today!

 

[AnOldUR]

I thought the same thing, but ran across them while grazing Amazon. Did a Google picture search and turned up this. If the rubber is soft enough, it looks like they would provide a good seal, but don't know.

 

[iamperplexed]

I use them and prefer them because they seal better especially when using my blow-off tube w/ copper elbow. My local brew shop sells them and they are labeled "musting caps" if I remember correctly.

They work great for my glass carboys but are a little difficult to pry off of a better bottle. In fact, most of the time I have to "roll" them back up over the neck if they won't twist off. As a word of caution, I was recently lifting a glass carboy by the neck and the cap gave. Luckily I was lifting out of a water bath and it only dropped a few inches back into the water. Close call, and I certainly won't do that again.