My guess is a custom piece. I think most pieces have a 0.5 mm give or take. Some jewellers have empty standard settings in their stock so if you want to be sure, bring the stone into the store to inquire.
Thanks Chrono! I was afraid of that!!! I wish I could just go to a jewlers and look at some settings, but we live in a small town and they would have to order some pieces in for me to check
. That is also why I have so many stone/setting combos sitting around-small town = scary options for setting stones! I usually just wait until I am headed back home to my old jeweler.
I’m so sorry. I have a 7x8mm setting and could not fit in a 6x8mm stone which is why my guess is that it will not fit. It took me quite a while to find the right stone.