5.5 but my ring is 5 and 3/4. At the time of resizing, we decided on 5 and 3/4 but a 5.5 would have been perfect. Getting it over my knuckle was the issue.
I wear a 6.5 ring although my jeweler suggested a 6. I'm afraid to size down, though, because I have prominent knuckles and my fingers tend to swell. I don't want my ring to get stuck.