New soft ones leak!
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.
Reviewed by: Mark from on 2/18/2016