I bought this in a XL(US L) and when I have it buttoned all the way up it looks and feels tight and too small for me. Sizing is tricky becuz I have gotten a few other shirts in this size and they fit perfectly! When I don't have this shirt buttoned all the way up tho it looks great! I'm just gonna keep it becuz I hate doing returns. My measurements are: 38-40in chest, 15 1/2in biceps, 30in waist and I'm 5'9, 170lbs.