Down Sleeping Bags
Sleeping bags filled with natural goose or duck down provide superior insulation (warmth) without sacrificing weight or compressibility. They also have proven to have a longer life-span than most synthetic bags. Down sleeping bags do not keep you warm when wet, though, so look for bags with water resistant or waterproof shells. For a detailed explanation of the different qualities of down and how it insulates, read more in About Sleeping Bags.