The Wisp works as a standalone summer mummy bag perfectly suited for warm nights, where typical 30-degree bags may be too warm. The fleece liner interior delivers a soft, comfortable layer next to the skin that doesn't promote sweat like some bags with nylon interiors. A dual zipper also allows the top of the bag to be opened, keeping the upper torso cool and the lower torso and legs comfortable. For nights when the temperatures dip below average, the Wisp can serve as a lightweight outer bag for lighter, higher temperature-rated mummy bags. This gives campers an easy way to adjust to changing temperatures without having to rely on a bag that may be too warm or too cool. 4900042 Charcoal/Red