I purchased these in black and storm, meaning to get two pairs in S but accidentally getting the black in XS. I'm glad I did! I'm 5'6", 126 lb, and usually buy XS or S depending on the brand. The S fits comfortably around the waist and the legs are loose -- perfect for lounging or sleeping. The XS still fits well around the waist -- only a tiny bit tighter -- and the legs are slimmer and more fitted. These I'd feel comfortable wearing around town, or even to work for a casual day, dressed up with a sweater. The material is soft and flowy. My only concern is the elastic wearing out over many uses and washes, with no drawstring to tighten, but I'm happy with the more refined, "these aren't sweatpants" look.