The mostly rectangular shape of the Big Agnes Lulu Women's 15 Degree Synthetic Sleeping Bag gives you room to sleep in more positions than just on your back mummy style. The Lulu's not a superlight expedition bag, but it does pack a punch with synthetic Integrity insulation that's warm to 15 degrees, as well as an Insotect Tubic vertical baffle construction that provides more loft, trapping more air and therefore supplying more warmth. It also stays warm when it gets soggy, something down insulation doesn't do. Since it's not made for super long trips, the Lulu sacrificed a little bit of weight to provide more room, with a rectangular shape and extra space in the hip and feet areas, which provides better warmth as well as a more comfortable fit. It saves even more poundage by eliminating traditional ground insulation, instead keeping you warm by requiring a sleeping pad that slides into the integrated pad pocket, insulating you from the ground more effectively than traditional constructions. It keeps cold air at bay with a no draft collar, zipper, and wedge to keep your mom, your sister, or your friend warm and on the pad all night long. Given its pillow pocket and soft nylon taffeta lining, they might just end up staying in it all day, too.