I am primarily a wool wearing outdoors person, but in the southeast in the summer - it's a bit much. Been looking for some decent synthetic tees for awhile, was really happy with this and the hoody. I have an athletic build with broad shoulders and thin hips and always have issues with sizing (by the time I fit my shoulders things are too big in the hips) - this was a pretty good fit for me. I like my T-shirt's pretty snug - it's a bit tight in the shoulders on me, but there is enough stretch in the fabric to make it work. OR walks a pretty good line between the hip/shoulder sizing in athletic wear. I am 5'6", 125# and went with the small. If you are like me, get two sizes and just see which fits you. I got a medium in the hoody because I wear it over other things. Good piece - wicks sweat really, really well.