how worn can a synchro ring be until it is considered "bad"? to the point where the outside is completely smooth or is there a different way to visually inspect it?

I think my synchros look alright, they all looked in the same condition so I'm considering to just put it all back together, run it in the car and give it a try. if it grinds or shifts bad, then probably get new synchro rings/bodys and bearings as a small rebuild.