The MILLE GTS STURMPRINZ Rain Jacket S11 wraps a fully waterproof, windproof shell around a 3L ATLANTIS membrane rated at 42,900 grams per square meter, high enough that sweat escapes as fast as rain stays out. That membrane covers the front panel, shoulders, and sleeve leading edges, while CORE Light softshell handles the rear body and sleeves for added stretch. A back vent opens automatically once the rider sits upright on a climb, pushing out trapped heat exactly when it builds up most. What Our Gearhead® Experts Are Saying:"I climbed hard in a downpour, and the inside of this jacket stayed as dry as the outside, no clammy base layer waiting at the top. That's the first rain shell where I stopped unzipping just to breathe."