The jacket stays dry on the inside during physical exertion. How does it work? The symbionic™ membrane spreads the water vapour and sweat over a very large surface area. The warmth on the inside of the jacket or trousers presses the moisture through the symbionic™ membrane to the outside where it can finally evaporate. symbionic™ is able to absorb moisture in the membrane when the body is sweating excessively. The jacket stays dry on the inside even under great physical exertion. Naturally, the symbionic™ jackets and trousers are completely waterproof and windproof on the outside.