A full-body bunker in the depths of winter, the Hyperdown 15 Sleeping Bag is the warmest sleeping bag we have ever made. Best-in-class Allied Down 900-fill goose down sets the standard for warmth-to-weight and packability, while the ExpeDRY treatment provides synthetic-like performance in wet weather. The 15deg bag is constructed to accommodate additional layers in your clothing system when the mercury plummets. Thoughtfully placed zippers free your arms to enable glassing or cooking and maximize time spent in warmth that you won't want to leave behind.