The Women's Flame Fm0 Sleeping Bag is the lightest in Sea to Summit's Flame collection of ultralight bags built for backpacking. This bag is particularly useful in that it can double as a liner for the other Flame bags for increased warmth. By itself, the bag's 850+ down insulation provides a comfortable temperature rating of 55F, which is suitable for the middle of the summer. The down insulation is so lofty and compressible that the bag weighs a mere eight ounces, and it can pack down to the size of a water bottle so you can take it on adventure races. Sea to Summit treated the down with Ultra-Dry for hydrophobic properties that maintain the down's lofty warmth in moisture-riddled environments.