When it comes to jackets for winter weather, how thick they are depends on where in the world you live. If you live in the frozen wastes, you need a thick jacket to keep you warm. Often those thick jackets are filled with down or something called Primaloft. Whatever is inside, they are bulky and difficult to pack away when you travel.
A company called NuTech has unveiled a new line of jackets called NuDown that promises to be very thin, yet keep you warm using nothing but air for insulation. The jacket in the image is an old model, the new version promises to ditch the bubble look and go with something smoother.
The jackets inflate using a squeeze bulb that looks like something from a blood pressure monitor. The company claims that each squeeze of the bulb is enough insulation to raise body temperature by 1 degree. The jacket can protect you and keep you warm in most winter weather. For times when the temperature is below 20F, argon canisters are available with an adapter to keep you even warmer. The big downside to these jackets is cost. They sell for $400 to $600 each.