They're supposed to release oxygen from the water with electrolysis rather than pumping air into the water.
I've got some as a friend recommended but he doesn't have diaries or comparisons so I was wondering what other anecdotal evidence there is. It doesn't appear as though the company is promoting their product in relation to this scene so there don't seem to be many people who use, or know, the product.
O2 Grow manufactures industry leading dissolved oxygen emitters. No other products delivers higher dissolved oxygen levels which makes O2Grow the best choice for improving plant yields.
www.o2grow.com