I own 3 of these and alternate them all winter long for my cold weather running. They're awesome to run in. They're super light (they are NOT puffy at all and that's the greatness about it. People on other reviews have complained that they are cheap material, no. This is how they are supposed to be and it's genius. The inner lining is a bunch of silver dots that reflect your own body heat back to you and that's how your stay warm! Can wear other layers under it and use it as a shell or can wear under jacket without looking like a marshmallow. Like I said, great running vest. Also, so many pockets!