This is an interesting item. I'm glad I got it, but I think that people should consider carefully why they are getting it. It is an alternative to your "meant to be destroyed" cotton clothing that you would wear at the crag. It fits like a comfortable athletic shirt, neither a base layer nor mid-layer. It's shear (yes, it is see-through, like a black undershirt can be seen through a white button up), and lightish, not ultra-light, just, not heavy. It's not hot, but not really cool. It's hood isn't huge, nor small, just big enough to fit loosely under a helmet. I thought it could work as a sun-hoody, and it does indeed, but not as well as a dedicated sun-hoody. I can run in it, but it's not light or cool enough to call it running gear. This is a warm weather climbing piece. It SCREAMS climbing. I haven't climbed in it yet (thanks Covid), but I feel secure in describing it as such. Get it for climbing.
Specifics: I'm 5'10", skiiiiiiny (145-150lbs, depending on my candy intake), broad shoulder and long arms. Nordic climber body. I got a medium. It fits like NWA items seem to fit, similar to OR but longer arms and wider on top. Long sleeves, doesn't constrains the shoulders, boxy. If you have the shoulder of a climber but emaciated body of trail runner, congrats, it will fit you but you won't fill it out. All I can ask for really.
M / Colorado Tuxedo Blue