The Thermolator sounds like the tough piece of equipment it really is. It's a level II, meaning it can solo as your only base layer during mild days or heavy output OR it can be your first layer under a much heavier base layer during really cold times. The 360 degree stretch jersey  material is one of our favorites because of it's supple softness. The anti-microbial treatment minimizes odor.  There is more technology in this fabric than you'll find in your kitchen!