Bob, I was able to fit two 6 ft. romex cables inside a 1/2" flexible
conduit with no problems. There is still plenty of space left. I can't
use Romex only because as far as I know, the local code doesn't allow
the use of Romex cable in high rises.

I usually use MC cable, but in this particular case, it was easier
because the conduit was already there.

Thanks..