Ultralight Sleeping Bag
Sierra Designs Mobile Mummy
$270, 2 lbs. 8 oz. (men’s regular)
Sizes: men’s regular and long ($290) and women’s ($300)
Stepping out of my tent on our first morning in Arizona’s Aravaipa Canyon in the first week of April, I was greeted by an air temperature barely above freezing and a steady wind sailing through our camp at about 20 to 30 miles per hour. So I reacted in the only way that made sense: I wore my sleeping bag in camp. And I could do that and walk around easily (while my friends assumed postures of cold discomfort wearing their down jackets outside—or simply stayed in their tent) because my bag was the Sierra Designs Mobile Mummy 15° F/-9° C.
I stayed warm wearing the Mobile Mummy 15° F/-9° C around camp on evenings and mornings in those temps and slept in quite comfortably in it—not even having to always zip it up completely while wearing just a T-shirt, underwear, and socks—on nights ranging from just above freezing to the low 40s Fahenheit. My wife found it more than warm enough on four nights backpacking in late summer in the Wind River Range, where the lows dropped into the 40s F—the kind of temps for which she prefers a 15- or 20-degree bag because she gets cold easily.
After removing it from their product line for nearly four years, Sierra Designs has brought back the Mobile Mummy (which I’ve reviewed in its previous version), updating it with 55 percent partially recycled, 20-denier nylon ripstop fabric with a PFC-free, durable, water repellent treatment (DWR). That 20-denier fabric is heavier and more durable than what you’ll see in many backpacking sleeping bags.
Remaining unchanged in the Mobile Mummy are its long, two-way center zipper extending to the footbox and the zipper-less armholes with overlapping flaps to seal out drafts while sleeping. The center zipper is not only great forside sleepers, it makes sense for most users and I’ve long wondered why that’s not standard in most backpacking sleeping bags. The armholes, of course, enable you to extend your arms outside the bag while wearing it.
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But understand that you still need a layer with warm sleeves on cold mornings—which means that a Mobile Mummy may not necessarily replace an insulated jacket, but it may allow you to bring a lighter jacket that’s augmented by this wearable bag. (You also may need an insulated jacket during the daytime or while on the trail and you can’t wear the Mobile Mummy for that—it would be far too warm and it doesn’t give your legs enough freedom of movement for real hiking.)
Most distinctively, when unzipped from the bottom end, the Mobile Mummy’s footbox can be lifted up and toggled to the outer shell so you can wear is like a very long down parka, even walking around camp in it. That’s why it made sense for SD to make the Mobile Mummy for sub-freezing temps (or even above freezing for users who get cold easily): On mild backcountry nights, you don’t need a wearable sleeping bag.
Stuffed with 18.6 oz./525g (in the men’s regular) of 800-fill power, water-resistant DriDown, the bag carries an ISO comfort rating of 27° F/-3° C and a limit rating of 16° F/-9° C. That high-quality down makes the bag reasonably warm for its weight and more packable than down bags with a lower fill rating and virtually any synthetic sleeping bag. The wide, front zipper draft tube is reinforced with stiff fabric to preclude any possibility of snagging, as are the ample draft tubes at the hood and armholes.
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With a fit length of 72 ins./183cm and circumferences of 60 ins./147cm at the shoulders, 58 ins./147cm at the hips, and 40 ins./102cm at the feet (men’s regular), the bag feels adequately roomy even as its mummy shape remains heat-efficient and minimizes bulk when packed.
The non-adjustable hood (read: no cords in your face when sleeping on your side) features enough elasticity for a snug closure around your head and face and to move with your head even with the front zipper quite open—as it did for me flopping from side to side during nights. That conveniently eliminates the step of closing and opening the hood when entering and exiting the bag; and by just opening the front zipper a few inches, you can easily push the hood off your head when needed.
The bag packs into a stuff sack measuring 8×16 ins./20.3×40.6 cm, which is compact for a bag this warm. It’s also available in a men’s long and a women’s model.
Sierra Designs Mobile Mummy 15° F/-9° C
The ability to wear the Sierra Designs Mobile Mummy 15° F/-9° C makes it one of the most versatile sleeping bags for backpacking, but its warmth, moderate weight, high-quality down, center zipper, and comfortable dimensions and hood offer more good reasons to get one.
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