This is one of the worst shirts ever received. Substantially undersized usually wear a L ordered XL to ensure fit and usable in S Texas heat and humidity. Fabric does not breath at all. Do not consider order at least two sizes over and only if live in upper northern areas
I tried this shirt out for the first time after a normal workout and I could tell a difference in my posture and blood flow in my back and shoulders. The shirt is a bit tight around the armpits, but after wearing it for about 30-40 minutes it did not seem so binding anymore. The shirt felt like it had a cooling effect on my body, it must be due to the moisture wicking material and breathability. The shirt was long enough to tuck into my pants and wear a collard or button up along with it. I am about 5'9" with a 32" sleeve 15 1/2 neck and 32" waist. If you are suffering from back or shoulder issues you should give this shirt a try; as it may help with your issues.
I bought these shirts for my husband and he really likes them. He liked the fact that they came in white so he could wear them under another shirt. He likes the way they feel and how they help him maintain good posture.
While I just put the shirt on today, I find it does what was described in the product discussion. Very comfortable and it is serving the purpose it is designed to do.