If you wear it under your jacket, though, you won't be able to reach the pockets on it, especially the ones on the side. You can put the tether strap out the top, but if you move forward at all, the jacket will be pulled back, something I'm sure no one wants in 0 degree weather! I'm 6' 4", so the system is a little further down my back than most peoples', and the tether strap connects a little below my shoulder blades, so any garment over it is not very comfortable. I always wear mine on the outside: easy access to all pockets, no need for carryin a gear bag, and no "popped collars."