I've read that, too. But my batches of wine are too small to fill a 5 or 6 gal. carboy, and 2 gal. of wine in a 3 gal carboy leaves a lot of air space. I figure if I can fill one of these 99% full - they'll be exposed to a LOT less air than if I have a partially filled 3 gal. glass carboy. How much O2 can actually migrate thru the plastic? Enough to oxidize the wine in the couple months before I bottle it?long term aging is plastic carboys is usually not recommended. possible air osmosis through the plastic. although the sellers of new PET carboys advertise as this is not a problem . I would question water bottles.