Hi Dave
I think they’re fab for storing in and using as a keg, but honestly I wouldn’t ferment in them again. They’re a right pain in the ar5ehole to clean! The opening at the top is tiny and to get the crud off the inside I have to use a long plastic spoon, with a micro fibre cloth and an elastic band over it! I had considered one of those spray cleaners but honestly I don’t think it’ll work for the sticky crud / krausen line that’s been sat in the fermenter for two weeks.
They do seal properly though and you can fit the black stainless fittings on the ball locks, as you can’t with those carbonation caps on the fermzilla. Up to you but that’s my view.
Whatever you do don’t get a junior. They’re crap!