What to look for in ring sling?

CarlaAndJames

I have an ergo and a moby, love both! I still use both with my 20 month old. We have a new baby coming in July and I'd like to add a ring sling, mostly so I have something easy to pop one baby on my hip for a minute, not for long term carrying.

What do I need to look for in a ring sling? Would prefer not to spend a TON (maybe $60ish max?), willing to look at used. I'm 5.5, but a size 12-14, big boobs, do I need to make sure I get it a certain length? Certain fabrics?