Great for ultralight backpacking, alpine climbing, and bike touring in warm weather, the Sea to Summit Spark SPII Sleeping Bag is filled with 850 Ultra Dry Down for incredible lightweight and packability.. . . . . 850 Ultra Dry Down is treated to repel moisture. Ultra Dry Down retains 60% more loft and absorbs 30% less moisture than untreated down. Contoured mummy shape with a full hood. Will keep you warm in temperatures down to 35AdegF. 10D UL nylon shell treated with DWR and a 15D nylon soft touch liner for lightweight durability. 13 length YKK zipper maximizes warmth and minimizes weight. Lightweight Ultra Sil compression sack and storage bag included.