The Viper 500 Down Sleeping Bag, from Vango, is a durable & extremely warm 90% duck down 3 season sleeping bag that has a four panel profiled hood with multi-cord closure for a warm, snug fit with an additional layer of insulation within the hood. Vangos Thermal Embrace System combined with its Omega shaping means that the Viper 500 Down Sleeping Bag provides better heat retention & provide warmth where needed most