In retrospect, I should have ordered a 12 though I can't recall if it was available at the time. I'm very small and thin so I rarely can find my size in men's and tend to buy boys' clothing, or women's if I'm shopping online since it doesn't really get noticed.I can wear this vest all day with little to no problems, and the quality of the material is EXCELLENT from what I can tell, but 10 is a little small even for me at 5'4" and approximately 114 LBS. When making my purchase, I was certain to measure very carefully and did take heed of the warning that the product may vary by up to 3 inches, but still wasn't sure if 10 would be right for me. It does feel very snug, and if I sit down I have to undo a button or two which isn't a huge deal, but taking a deep breath in this thing is a little difficult. So take my advice and if you're purchasing this for your child or yourself and you're between sizes, go up. I'd still like to give this product 4 stars for the exceptional fabric quality and how comfortable it is despite it being very tight on me; it's not fully the supplier's fault about the sizing, but I took the star off just because it was a bit unclear.