Im 5'6 and kind of thin and I got a medium. Its a perfect fit and not really oversized which is what I wanted. Its really good quality and exactly as pictured.
i got this in a size m dark gray and it fits loosely and exactly as desired. for reference, i’m 5’0 ft and 98 lbs. the vest also came smelling quite nice in fact and there were no loose threads. this product was selling by another seller for 30$ on the site but i’m very glad i took the risk to buy this for cheaper, the quality is very good and overall fantastic.