Ski touring and mountaineering demand a down sleeping bag that is comfortable in the coldest months of the year. The Therm-a-Rest Altair is designed to provide efficient warmth down to 0 F (-18 C), while offering light, packable performance that makes each day in the mountains more enjoyable. Like all Therm-a-Rest sleeping bags, it integrates with your mattress (sold separately) to eliminate the sliding, twisting and cold spots that can interrupt sleep. Also features draft tubes & collar, snag free zipper, stash pocket, sculptured hood and trapezoidal footbox.