The Twilight is a mummy shaped, multi-function piece for year-round use — as an accessory or as a standalone bag. Used as an accessory, the Twilight can serve as a liner or an over bag for your favorite sleeping bag. Using this bag is quick and easy — slip it over top of your sleeping bag to use as an over bag or slide it inside of your mummy bag to use as a liner which will provide added warmth for the frigid nights in the outback. When used as an over bag, the Twilight even offers ample room for both a mummy bag and air pad. As a standalone bag, the Twilight is perfect for warm temperatures in the summer, when you only need a very lightweight bag. The Twilight is constructed with a polyester outer and has a soft, cozy fleece interior to help maximize your comfort. You can't go wrong with this year-round versatile bag!