I am 5'9" 150 lbs and ordered a small based on the reviews. I could have ordered a medium and still been fine, and wish I had because the sleeves are a bit short for me and I wouldn't have minded a bit more room around the chest. The quality seems fine and you can't beat the price. I use it for Microbiology and it seems to be like the ones they sell in the bookstore, only $15 cheaper.