I wore this top for the first time in an Ironman. It kept me warm when it was cool outside and cool when it was hot out. I have no idea how that works; it just does. I wear it now in every 5K, 10K, 13.1 or 26.2 where I need temperature or sun protection. When it's less than 70 degrees, I won't run in anything else. Period. It fits tight. It's supposed to. It's a second skin. I see other reviews that would like a pocket, but the pocket would defeat the design of the top and make it saggy in the back. I wore this for the Boston Marathon, NY, Berlin and Disney marathons -- it dries out quickly enough that you can wear it for a race one morning, wash it, and be completely confident it will be dry for the race the following morning.