During a normal night, a person releases up to 500 g of sweat in the form of water vapor. This moisture - should it remain in the insulating material of the sleeping bag - causes a drastic decrease in the insulation ability. At very low temperatures, the dew point (the temperature at which water vapor becomes liquid) is usually on the inside of the outer shell. In extreme cold, this condensation can even freeze to ice, which means that the filling can not dry in the long run and the sleeping bag is getting heavier and wetter. This leads to a drastic slump in the insulation capacity of the down sleeping bag.
This system uses a second inverted outer shell made of water-resistant and breathable Shellproof Ultra. By means of a corresponding zipper opening, this layer can simply be turned outward to dry. Ice crystals or drops of water that have formed between the sleeping bag covers can be easily shaken off. In order to achieve a faster drying of the remaining condensation moisture, the inner sleeping bag cover consists of down-proof, but extremely breathable Shelltex Ultra. The additional air layer between the outer shells increases the heat retention capacity, thereby achieving a sensational heat-to-weight ratio.