I got this shirt as a promotional gift a couple of years ago when I bought another OR product. It was an amazing "find". I am one of those people that are freezing all the time and I live in a place with pretty harsh winters. All of a sudden I could be outside in the snow with my dog for hours wearing just this shirt and a ski jacket. The shirt is very comfortable, light and soft, yet it is very warm and stylish and it provides the ultimate insulation. You can wear it as your second layer or just wear it by itself any place that calls for casual clothing. As far as fit goes, an M fits me pretty snug and I am 5'7" and weigh about 125. It is not very long, it doesn't go down to my hips and I can't really use the thumb holes in the sleeves because that becomes uncomfortable; the sleeves are a bit on the short side. Bottom line, it's a great product, just if you're on the tall side like me you might wanna get a size up.
I own the Radiant LT Zip layer in multiple colors and I have bought as a gift for multiple friends, both male and female. It's a fantastic addition to layering. Low profile collar fits under jackets without neck bunch. Fit is trim, allowing for a great fit under a jacket or down layer. The fabric show minimal piling after, literally, years of washing. I have one that is 4 years old at it looks every bit as good as the new one I purchased this year.
"Best warm layer i've ever owned- never leave home without it"
I've been wearing these for years- in fact, I get one or two each season so I've got a hefty collection. I'm always cold and for my sport (rock climbing) we are always chasing cooler temps. I love this top for climbing, it's warm, durable, flexible (moves with me) and it's got a little neck that I can zip up to keep me really warm or unzip if I'm feeling a little hot. It washes well, wears well and is all around super functional. I literally wear these tops every day that I go out climbing!
This shirt is so comfortable as a base or second layer and it has held up through a lot. It's been on several camping and backpacking trips and survived a month of field work. The zipper works flawlessly and the thumb holes are awesome. I got mine in black and it looks great. The only downside I can see is that it's starting to pill a bit around the elbows, but I have used/washed it a ton, and despite this it still looks great unless you are looking for the pilling, which chance are only I am. Cannot wait to save up some cash and get another one of these in a new color :)