The Jack Wolfskin Mens Atmosphere Jacket in this Poseidon Blue colourway is an ultra-light down jacket with a premium quality duck down fill that will keep you warm in sub-zero temperatures. The STORMLOCK shell boosts the insulation performance by blocking the cold winter wind, while light showers simply bead up and run off the surface of the fabric. And if you get too warm, simply stash it in the stuff sack and drop it in your pack.