I love this thermal layer shirt

I've had mine for almost a year now. I recommend it wholeheartedly. I use it for an inside layer when I ride my bike, run, or hike. It fits snug to the body and traps warm air in while allowing your skin to breathe. Sounds like a commercial, I know, but that's exactly what it does. I don't wear it in the sun or on warmer days. I've found that the combination of it being black and the insulating properties can get a little too warm.