The Cinnabar range of sleeping bags is the warmest range from Big Agnes and this Cinnabar Sleeping Bag is the warmer of the two. Its sub-zero rated down insulation is intended for expeditions like 8000m summits self-supported missions across Antarctica and all-around winter camping and backpacking. Despite being the warmest the down insulation is surprisingly light lofty and packable. Big Agnes treated the down to retain its lofty warmth if it ever got wet which would be difficult to do considering water-resistant windproof Pertex Quantum protects it from winter’s weather. The footbox features a burlier Pertex Quantum Pro waterproofing that comes in handy when moisture inside the tent drips down the walls and onto your feet.