Devin B.wrote a review of MontBell Ultralight Thermawrap Insulation Jacket - Men's on April 20, 2009
"170#, 5'8" athletic: I got the medium, it was a little short and wore like a shirt, but the real problem was the arm pits fit very tight, too tight for adequate mobility. Will size up to a large and see what happens. Lost star for fit."
Sized up, and had perfect fit. No further complaints, great piece of gear.