Goose Down Sleeping Bags traps warm air in the sleeping bag and is lighter. Down Sleeping Bags are marked 600-fill, 700-fill and 800-fill This is the amount of space that 1 oz. of down will occupy. The higher number of fill power is less amount required to fill the same space and makes it lighter. Down sleeping bags will last longer when taking care of. Down sleeping bags will extend the back packing season a few weeks longer.
