I am a very skinny guy, 6 feet tall and weigh about 140 pounds. I wanted a striped shirt that would have a little freedom of movement and I thought a medium shirt would work for me, but it was embarrassingly square and large on me. Fits almost like XL! I applied and was about to send it back but offered it to my roommate first to see if he would like it as he is a little more average built than me. I washed it, threw it in the dryer and decided it didn't need it as it had been sitting a lot. However, comfortable enough, now it fits me very well! I love wearing it! Long story short, for an average height person (my roommate is about 5ft 10", 150lbs?), medium fits very well! But I definitely recommend washing in cold water and hanging to dry to prevent shrinkage. For a really slim, reasonably tall person, the medium only worked well AFTER it had been set, washed in hot water, and toasted in a dryer.
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