I'm not familiar with that brand or designation, Danita, sorry, but I'd guess that anything designated with a 3 would be coarse, but not quite as big as large. Large-sized pieces might typically be used as "glowing embers" in a faux log stove, but would probably be a bit too big for finessing sprouts out of containers without damage.
Finer vermiculite can work too, but I think moisture levels have to be more precise when using the closed container system. I have sprouts in the fine stuff now, but when I remove the covers to check on those there is a disquieting odor to it. Not quite an odor of decay at present, but maybe a precursor of it. Whenever there's a choice involved, I'll use it for very short germination/duration type sowings, and get the seedlings out of it as soon as possible.
I'm growing more and more sure each time I buy it that I'll only trust what's inside if I open a bag and look.
