A mission-critical piece designed for high-altitude expeditions and the most bone-chilling conditions on Earth, the Phantom™ WINDSTOPPER® -40° is our most protective sleeping bag yet. Take shelter from hardcore mountain conditions in this weather-resistant GORE-TEX cocoon that's so ultra-warm and packed with lofty down insulation, you won't want to leave when the summit window strikes. Built with light and compressible materials, moving camp is a breeze, helping get you one step closer to the top.