TNF website wrote:The North Face Inferno -40F/-40C is a new down expedition sleeping bag for the lowest conceivable temperatures explorers are likely to experience. For polar or high altitude travel including Himalayan winter assaults, this lofty 850+ fill goose down bag is engineered and baffled to lock in heat. A Pertex Endurance shell repels moisture and condensation keeping the high loft down dry and effective. Designed to defy heat sapping climates with an ergonomically shaped fitted hood and roomy footbox construction, body mapped compression pads to reduce dead spots and with clever trapezoidal baffles that maintains the insulation volume and hence warmth. The compression stuff sac doubles as a summit pack. Clever. The North Face Inferno -40F/-40C is a best-in-class down insulated expedition sleeping bag badged with our trustworthy athlete tested, expedition proven Summit Series™ kite mark.