I already own a Coolibar jacket in size medium. I ordered two additional jackets in size medium. One is a perfect fit, the other is much too large. The customer service rep could care less about their company's inconsistency in sizing and told me to "gift it"! She subsequently told me that it was meant to be worn over a sweatshirt or something similar. If I was wearing a sweatshirt, I wouldn't need a sun protection jacket! Buyer beware with this company.