after being disappointed by my local grocery store brand, I learned that the Wally brand was RO. I've been using it happily ever since in my 18.5 WSM. a full ring w/a full load in a non-weber chimney gives me consistent temps and good longevity. I get multiple cooks out of a full ring just by knocking out the ash and adding a chimney of lit.
that being said, I have yet to christen my 18.5 ots. so I can't comment on how it works in a grill vs smoker.
All Weber, All Charcoal-18.5" Kettle, Go Anywhere, Performer, 18.5" WSM, NYG Smokey Joe