...however I noticed that if a guy (or gal) wanted to use an auto-siphon you are outa luck with the big mouth. The advertisement, well, catalog description notes the Big Mouth Bubbler was "created by homebrewers for homebrewers", or something close to that, but the noted homebrewers apparently do not use auto-siphons as they will not fit in the smaller sized stopper hole.
As a side note, although related, why is it that every fermenter has some sort of G-D'd proprietary (or otherwise) short coming? The Speidel's spigot will leak, at least mine did (I rigged a fix for it) as it did for a number of others per the reviews at MoreBeer. The big mouth as a stupidly smaller stopper hole/stopper arrangement, no doubt to sell a few extra flipp'n stoppers. Plastic scratches. Glass carboys cannot be easily cleaned. SS is expensive and I'd bet a dollar there are some issues with one aspect or another on the Brew Bucket... The Big Mouth was a great idea cut to 'just another idea' due to the lid, IMHO.