This 3-season sleeping bag is wide, warm, and packed with features. With a 3-dimensional full down collar, a full-length YKK zipper, and 5? of loft, the AlpinLite has quickly become one of the most popular models. Western Mountaineering's award winning UltraLite has been a favorite among lightweight backpackers for more than a decade. The AlpinLite is just a wide version of that great bag. While there are many 20 down sleeping bags on the market, none have the width, warmth, or loft of the award-winning AlpinLite.