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IN THE STORE Claustrophobes and warm sleepers should make certain that their ultralight mummy-shaped bag has a full zipper—to shave ounces, some go only halfway, while others dispense with a zip altogether. Look for loops designed to lock your bag to your sleeping pad. A hood and a draft collar—an extra ring of insulation at the neck—add tremendous warmth. Down is pricier than synthetic fill but lasts longer and has an unbeatable fluff factor. Just don’t get it wet.
IN THE FIELD If base-camping for several days, banish your inner neatnik and leave your bag splayed out to encourage air circulation and drying. A couple hours of full sun will help fry odor-causing bacteria.
IN THE FUTURE Given the recent convergence of electronics and gear—witness Marmot’s electroluminescent Phenomenon EL Jacket—it’s just a matter of time before sleeping bags catch some juice. Imagine a sack with a small night light built into the hood for bedtime reading. Or picture a small heating element in the footbox to toast your toes on a chilly night. Batteries not included.