The Bristlecone SMF -10 Degree Sleeping Bag (6' 6") is built big and warm and big. 69" of girth at the shoulder and 48" of girth at the foot. Crammed with 42 oz of 850+ down yields an unrelenting 8 1/2" of simmering loft that keeps you heated to -10 degrees . A large draft tube and the down filled Super Collar make certain that winter remains outside. With 2 zippers it can be zipped to our mummy bags or unzipped to lie flat. In spite of its house sized proportions the Bristlecone weighs only 4 lb 2 oz.