The Sierra Designs Mummy 800 Sleeping Bag has some unique features that'll knock your socks off. Or rather, that'll let you keep your socks and shoes on. Like many down mummy bags, the Sierra Designs Mobile Mummy 800 Sleeping Bag is light enough for backpacking trips and warm enough for temperatures as low as 30F. Stuffed with 800 fill duck down insulation, this lightweight bag has an excellent warmth to weight ratio, and it stuffs into a small corner of your pack so you can easily bring it along. Unlike many down bags, however, Sierra Designs added its proprietary DriDown treatment to the down for water resistant protection if you're camping in wet environments. And unlike most mummy bags, the Mobile's unique design allows you to sleep on your side and stomach as well as your back. Sierra Designs also reinforced the hood and draft collar with insulation to prevent cold air drafts while you sleep. Ok now for the socks and shoes part. Unlike almost all sleeping bags, this bag can travel with you out of the tent and around the camp so you can be warm when you're star gazing at night and when you're sipping your breakfast beverage and watching the sunrise in the morning. To gain mobility, just push your arms through the zipperless armports and slide your feet through the center, two way zipper. Then attach the footbox to the bag just above your knees so it doesn't drag on the ground while you walk around. When you're up and about in this bag, its design makes sure the bag rests on your shoulders like a jacket instead of resting uncomfortably on the hood.