Pulls sweat away from the body. I don't run without it(i could, but i don't want to) Just make sure you correctly measure your chest and waist before buying the shirt.

Also, the compression is already accounted for in the size chart. For example, i have a 44 chest and i wear large. When the shirt i ordered arrived it looked like a small shirt, but once i put it on it felt just right without being too tight.

Measure, buy, and enjoy.