Reviews for whatever reason are not available to me so I will post my thoughts here. I normally wear a large at the moment but bought a medium as I'm losing weight. The medium size fits like a very big large, maybe XL. I have XL shirts that are smaller. The sleeves are comically long. I can't comment on the quality yet as I've worn it once, but I can say it is the ONLY merino product I own (in fact I wore an IceBreaker Tshirt under it today as my commute started right at the freezing point) that stinks. I wore it for less than 1 hour and it smells. It's on the coat rack at my desk about 4 feet away and I can smell it from here.
Unless you have a thing for crazy-randomly sized stinky things, spend your money elsewhere.
Based on this one product (actually 2 as I bought one for my wife, too) I cannot understand the fuss about this company's products and I will never buy anything else from them again.