Slumberjack Sojourn 40 DriDown Mummy Sleeping Bag Dri-Down insulation: Down is treated with a molecular level polymer to create a hydrophobic finish on each individual down plume. This finish allows DriDown to stay dry longer, loft better, and dry faster than untreated down, keeping you warmer in any environment. Dual 57" long zippers with two sliders each provide unequaled venting options. External hook & loop tabs combined with dual zippers create "arms out" functionality. "Double-Dri" waterproof panels on the hood & footbox provide additional water resistance. Black colored "Solar Liner" fabric allows fabric to dry more rapidly in the sun.