Here come the Ho-Ho-Holidays!
"Followed the Size Chart and originally bought the L and was swimming in it. I am a slim Medium (6ft - athletic 170lb) through and through and I could still have the Medium taken in around the middle. I'm happy with it all the same. Sleeve length and leg length are perfect, not too short even when you raise your arms over your head. I knew what I was buying and am happy with it."