Originally Posted by andrew.roos
The pentahydrate (5 H2O) is the familiar one ("hypo") so I would get this; I'm not sure whether the 6 H2O is genuinely different or just a typo by the seller.
Edit: I see they both state they are pentahydrates, so presumably it's a typo. But I'd still be safe and get the one that is correctly identified (5 H2O).
I have contacted the provider for details, the 6 H2O is much cheaper :-) Thank you!