Wow, these run very large. I almost sized up to a medium based on other reviews but I'm glad I didn't. I wear XS-S in most tanks so I ordered a small and they are rather large. I am 5'2" 128# and a 32D. These almost cover my whole bum. I think they are supposed to fit this way though... For the price they will do the job.
The fabric is very thin and breathable. Seams are pretty good quality
After wearing it to the gym, they really are very large. Unfortunately they don't offer an XS at this time. They are very low-cut and really show a lot of cleavage at top so wear a high-cut bra with this shirt.
I bought a Small but it fits like a Large!