I'll be happy when/if GV gets the mini square Vision stardusts to go with this - that will be perfect for me. I have the tank system and I'm not happy with using the tanks - too small, and now I'm finding that after one or two fills, it's just not working/tasting the same. So for now, I'm not using the cap at all - just the 510 adapter with any of my 510 cartos/Vivi Nova/Stardusts, etc.