I wear a medium from underworks and got the small from GC2. I measure 35 around my chest and the small is for like 35-37. I'm wondering if I should have gotten an XS. But I'm 6'3 I haven't worn an extra small since middle school. It's definitely more comfortable than my underworks. And I've slept okay in it when necessary, but my underworks bodysuit makes me much flatter, and I can shift my chesticles so i look like I have pecs. In the GC2 they still look round, like breasts, instead of more square. I needed to replace my bodysuits because I've had them for sooooo long. Thought I'd try GC2 because they're supposed to be more comfortable. Now I kind of want new bodysuits but don't want to spend the money. But Top Surgery is still another 6+ months away. I think I have to suck it up and splurge.