I'm a male, 6 ft, 190 lbs, athletic build. The medium size fit perfectly.I bought this as my base layer for a winter adventure in northern Alaska expecting temperatures between 0 to -55°F. I've never worn a shirt like this before. Nice and warm, with 300 grams of material per square meter (gsm), making it pretty thick and you could even use it as PJs, hanging around the house, it almost looks like a super hero costume (wife laughed) instead of underwear. It's comfortable, fits almost like a glove with unique stitching in areas so it's more maneuverable, but does not feel tight like some other thermals do. It's a bit longer than a regular t-shirt and a bit longer in the back with the idea being that you will be tucking this shirt in and if bending over you won't get a draft of cold air/rain or snow/ice up your back that can cause back pain (which I have) and joint pain and swelling. The material on the inside, polypropylene, feels very soft. Polypropylene is one of the main reasons I was attracted to this shirt (and pants). I've read many benefits of it, being a superior material for warmth, dries very fast, wicks moisture away from the skin, and is very durable. Many recommended this type of material in your shirt when in cold conditions doing anything from standing around in the cold night (or gazing at aurora borealis) or being active under the sun (like skiing). The shirt has a second layer of polyester as the middle layer and a third outer layer of wool, which is where the 3-in-1 comes from. I love wool (breathability and insulation) but personally I cannot tolerate any wool, including merino wool, directly on my skin without feeling even a little bit of an itch. So with the wool being on the outside, no problem. They designed the top wool layer like a diamond pattern with air pockets to be able to trap heat, similar to how down feather shirts/jackets work. The wool seems durable with no signs of wear. As far as odor goes, I don't have a problem with it, in fact I don't even use deodorant when just around the house doing whatever and my wife can attest there's no problem, ever. So I cannot comment yet on how many times you could wear this before the silver-ion finishing, that's supposed to eliminate odor causing bacteria, kicks in. I tend to try to wash things after one use if directly on my skin whenever possible (whenever means I may not have a washing machine in the North Pole).I decided it was time to buy a high quality shirt (bought the pants too) and do away with my other thermals that just don't hold up. I plan to use the Thermowave shirt and pants for work when hiking and ATVing through the forested mountains in the rain and cold.MGoodWorth the money