The La Sportiva Mythic Primaloft Jacket maps its Primaloft Silver insulation by zone, running heavier through the body and lighter at the underarms and hood, so warmth builds where a body actually loses heat instead of everywhere at once. VapoVent construction moves that heat and moisture out during hard efforts like skinning uphill or a fast approach. Stretch panels through the sleeves and sides keep the fit moving with the body rather than against it, so a full range of motion never feels like a fight with the jacket. What Our Gearhead(R) Experts Are Saying:"I climbed a long skin track hard enough to work up a real sweat and never had to unzip to cool off. That's the zone mapping doing its job, not just a warm jacket getting lucky."