Standard Carboy Cap - 3/5/6.5 gallon glass carboys

Got it for a spare but not the same quality as ones I've purchased from others. Loose fit on my 3 and 5 Gal. glass carboys. It will be a last resort use.

It's a bit too large and therefore doesn't seal properly. However, this can be easily remedied with a hose clamp.

Very cheap soft plastic that bends/crimps when blowoff tube is attached. Does not seal well on carboy. Get the better quality ones from somewhere else.

I have several of the harder plastic ones that work great. These new ones with a R&L, or RoZ logo molded in them are softer plastic and leak. I fermented 2 carboys together, same recipe, same brew, same yeast starters, and same fermentation temp only the one with soft type showed no CO2 activity. I had a previous identical twin batch with one of the carboys having slightly lower attenuation than the other. Don't have enough data to support but I believe this leaky cap might be the culprit. 5 stars for the old plastic, 1 star for the new ones because they leak = no air lock.

I bought this and I don't like it seems loose it just can't keep out air being this loose. It's a little snug but not enough would not even think about putting a blow off tube on it.