THIS RUNS SMALL. I'm about 125#, and I got the large. With that being said, you can definitely adjust this thing a lot. I'm just glad that I got the large, so that I didn't have to completely loosen the tie in the back. I got this for a Murder Mystery party, and it was sort of in the theme of Game of Thrones. I was having hard time finding something that looked like body armor, and even more difficult was finding something that could properly fit a woman rather than a man. I settled on this, and I'm glad that I did! I won best costume. :-)