Two-Season Sleeping Bag
Sierra Designs Mobile Mummy 800 (30° F)
$330, 1 lbs. 12 oz. (reg); $350 (long)
Sizes: men’s regular and long, women’s regular ($370)
It’s a chilly morning in the backcountry and the last thing you want to do is exit your warm sleeping bag to step outside. With the Mobile Mummy 800, you don’t have to—you can wear your sleeping bag outside to fire up breakfast or take care of other business. Although the concept of a wearable sleeping bag that converts to a long down jacket isn’t new, Sierra Designs has achieved a nice kind of perfection with the Mobile Mummy.
I slept—and lived part-time—in this bag for three nights of camping at Idaho’s City of Rocks National Reserve, when the low temperatures ranged from the mid-30s to high 40s Fahrenheit. I slept in a tent but always got up and out of the tent early in the morning, in the coldest hours of the day, when we had a lot of wind. The bag seems true to its EN comfort rating of 39° F and limit rating of 29° F: I sleep fairly warm, but didn’t even have to zip the bag up completely or seal up the hood on a night and early morning in the mid-30s (I wore a wool hat outside).
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The design is so simple it’s a wonder we don’t see more bags that convert to down jackets (and my friends were coveting the Mobile Mummy when I wore it around camp). Zipperless arm holes allow you to stick your arms outside the bag; the holes are large enough for full range of arm motion, and have overlapping fabric to completely seal out the cold when you pull your arms inside. The two-way, full-length center zipper lets you stick your legs out of the bag’s bottom, and toggles secure the bag’s foot end up behind your butt, allowing you to walk around naturally. The result is a hooded down jacket that extends below the butt—very warm, especially with the hood up. It’s missing only sleeves, of course, so I needed a warm base layer on cold mornings. I like center zippers because they’re easier to open and close; and I’m a side sleeper, so a center zipper tab doesn’t dangle in my face like a side zipper.
The bag is stuffed with water-resistant, 800-fill DriDown insulation, which retains its ability to insulate even when wet and dries more quickly than traditional down feathers. I only experienced a brief, light rain shower while wearing the bag on this trip, which had no effect on the bag’s warm or loft. The bag is roomy while still fitting like a jacket when worn as one, with space for wearing warm layers. The hood forms a clean fit around my face when I seal it up, and closes up tightly, more like a sleeping-bag hood than a hood on a down jacket. It comes with a 14×7-inch stuff sack, but can be packed to about the size of a one-liter bottle with a compression stuff sack.
Besides negating the need to carry a down jacket of comparable warmth—eliminating roughly a pound and some bulk from your backpack—and the convenience of not having to get out of your bag to get up on cold mornings, its long length makes it warmer than a standard-length down jacket. Other than the disadvantage of having a long “jacket” with a bulky back side that occasionally gets in the way—when squatting to relieve yourself, for instance (you have to either carefully hitch it up or just take it off)—there’s hardly a downside to the Mobile Mummy. SD also offers a 15° F version (men’s $380, 2 lbs. 4 oz. regular, $400 long; women’s $420, 2 lbs. 7 oz.).
BUY IT NOW You can support my work on this blog by clicking this link to buy a men’s or women’s Sierra Designs Mobile Mummy bag at moosejaw.com.
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See my review of another convertible bag, the Exped DreamWalker 450, all of my reviews of sleeping bags that I like and all of my reviews of backpacking gear, and my articles “Pro Tips: How to Choose a Sleeping Bag” and “10 Pro Tips: Staying Warm in a Sleeping Bag.”
See also my stories “Buying Gear? Read This First,” “5 Tips For Spending Less on Hiking and Backpacking Gear,” “The Simple Equation of Ultralight Backpacking: Less Weight = More Fun,” and “Ask Me: How Do We Begin Lightening Up Our Backpacking Gear?”
NOTE: I’ve been testing gear for Backpacker Magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See all of my reviews by clicking on the Gear Reviews category at left or in the main menu.