Sierra Designs Mobile Mummy Review

They’re here – after months of waiting, Sierra Designs’ innovative new line of sleeping kit has hit the market and our testing trips.  The Backcountry Bed, Backcountry Quilt, and the Mobile Mummy all offer unique advantages to backcountry sleepers.  Today’s tester is the Mobile Mummy, a product as highly unusual as it is highly functional.

Sierra Designs Mobile Mummy Sleeping Bag Features:

• Ultralight jacket hood
• Zipperless arm ports
• Garment-style shoulder design
• Centrally-placed, ventable zipper
• Draft collar, tube and curtains
• Stowable footbox
• 2lbs 4oz
• MSRP: $379.95

Mobile Mummy walks like an Egyptian, sleeps like a king

When Sierra Designs debuted their new range of sleeping bags, the outdoor world was on fire with images and brief snippets; I’ve been eagerly anticipating testing them out and we have the Mobile Mummy and a Backcountry Bed in for review.  The exciting thing about this is that the following review is one of the very first full-coverage pieces for the Mobile Mummy, and the Backcountry bed should be following shortly.  So, remember folks – you read it here first.

When I first received beta on the Mummy, my initial thoughts were excited but skeptical – I like the idea, but is it possible to create a truly technical, lightweight bag with a feature set like this?  Surely those arm ports are just going to leak heat all night long.  I’ve spent around a month testing the sleeping bag in lowland Spokane’s cold, wet Spring and Nevada’s frigid alpine unpredictability – these locales demand versatile gear and they really highlight gear’s strengths and weaknesses.  Do you want the spoiler without having to read the rest of the review?  Well, I’ll give it to you – the Mobile Mummy, through brilliant design, manages to be both ultralight, technical and quirky.  It’s a true three season sleeper with performance on par with any conventional bag.

From a distance, I suppose the Mummy looks pretty normal – it’s longish and seems puffy enough.  That’s about where the resemblance to traditional sleeping bags ends, though: the bag is built with the zipper on the top instead of the side, arm ports and a jacket-style hood.  The whole idea behind the Mobile Mummy is that it doesn’t restrain the wearer like normal sleeping bags do – it’s designed to move with you while you sleep and then, in the morning, you can use the arm ports to do camp chores or heat up last night’s dutch oven Beef Wellington.  That’s the gist of it, anyway.

Yeah, but will it keep me warm?

The immediate concern that pops into peoples’ heads is whether or not this sleeping bag will be thermally efficient – that is, with all of its unique features, does it still perform the job of keeping you warm?  I was dubious going into testing, and it took some severe Spring weather to reveal the answer.  On a cold, snowy night at around 8,000 feet in the Ruby Mountains all of my doubts came to a head — and the Mobile Mummy passed with flying colors.  The arm ports have a very carefully designed draft curtain that seals up instantly while still allowing you to easily move your arms in or out.  Sierra Designs took care to make sure that the arm ports are long enough to let you easily get your arms in and out.  The curtain is designed to self-adjust once your arms are safely back in the bag so you don’t have to fiddle them into place – it’s clever and it works very well, but don’t ask me exactly how.  It works, though.

The next potential source of wasted heat is the top-mounted zipper.  Sierra Designs built in an excellent anti-snag track onto this two-way zipper, which is aided by the thickened fabric on the back of the draft tube.  The zip pulls easily from both directions and snagging is only a minor problem; what’s more concerning, though, is the possibility of heat leaking out since all of that thermal energy wants to rise up right through the zipper.  Sierra Designs’ solution is a pretty standard draft tube which does the job well enough, but it’s a little disconcerting.  A conventional side zip places the baffle mostly out of your way, but I found my hands touching the cold zipper and fiddling with the draft tube quite a bit.  The draft tube does a great job of preventing heat loss, but you’re definitely aware that the zipper is on top of the bag.  This is simply a natural consequence of the design, and Sierra Designs has executed it as thoughtfully as one could wish.

One of the many unique parts of the Mobile Mummy is that it has a jacket-style, ultralight hood and that the bag is designed to rest on your shoulders rather than your head.  The jacket-style hood is devoid of any shock cord adjustments and it’s a pretty conservative, close fit around the face to keep warm air in.  On one hand this is nice because there are no cords to strangle you and there’s also no thin shock cord to cut into your face – but, you sacrifice some control.  The brim of the hood is lined with a soft fabric patch that helps manage moisture as it builds up during the night.  The area around the face is very important in sleeping bags, and Sierra Designs nails it.  The zipper is covered over by a honkin’ enormous zipper garage and the whole dealio is sealed around your neck with a puffy, highly effective baffle.  Here’s a big statement: of all the sleeping bags I’ve used over the years, the Sierra Designs Mobile Mummy has the most comfortable hood.  Way to go, SD!

Is the Mobile Mummy a sleeping bag or an oversized puffy jacket?

The benefit of having the weight of the bag rest on your shoulders becomes apparent as you use the Mobile Mummy for what it’s actually for – grooving and gyving.  The two-way zip lets you slip your feet out and there are purpose-built toggles on the bag to secure the toe box up and away from your feet so that you can walk unencumbered.  When the bag is in this configuration, it becomes easy to perform camp chores or go pee without leaving the comfort (read precious warmth) of your sleeping bag while not being impossibly encumbered.  In truth, the toggles are pretty tough to fumble with at night or with gloves on – I’d like to see an easier system, but that would probably result in an unwanted weight gain.  The other great advantage about the Mobile Mummy’s fit is that it tends to move with you very well when you sleep – the front-mounted zipper and more natural body shape doesn’t twist around like conventional designs tend to, and I could comfortably sleep on my front, back and side in the Mummy.  That’s definitely not a trait seen in conventional bag designs.

One point of interest is the polyester fabric SD chose to built their new bags out of.  Naturally, the Mummy is stuffed with hydrophobic, 800-fill DriDown which we’ve tested before.  The down performs really well when wet compared to untreated down, but synthetic is still king moisture management.  However, SD built in an extra line of defense by using polyester fabric, which is naturally more hydrophobic than nylon.  Nylon tends to hold more water in its fibers, but it is more durable than polyester.  Both are thoroughly downproof and relatively lightweight; at 2lbs 4oz, the Mobile Mummy is pretty competitive in the ultralight category.  So, polyester – Sierra Designs is making the switch but most companies are sticking with nylon.  Only time will tell how big of a factor the marginal losses in durability will prove to be.

In my month of testing, the Mobile Mummy has seen its fair share of trying backcountry conditions but I’ve also engaged in a decent amount of horseplay in it – after all, when you can stick your arms out and walk around in a big cushy bag, what else are you going to do?  Anyway, the point is that the product has held up well so far.  There is no blown stitching on the arm ports yet and the reinforced fabric in that area seems to be holding its own.  The baffle design is simple and no-frills, but it serves its purpose well for a three-season bag.

The Good

• Believe it or not – it really is thermally efficient
• Thoughtful arm port placement makes it easy to slip in and out
• Top-mounted zipper and shoulder design help the bag move with you while you sleep
• Anti-snag zipper trap is works like a charm
• Jacket-style hood is simple but very warm and cushy
• DriDown continues to impress

The Bad

• Toggles that hold the footbox up are tough to wrangle with cold hands or gloves
• Front zipper’s draft tube is easy to bump out of place
• Simple hood sacrifices customization

The Bottom Line

The Mobile Mummy is a ton of fun while still offering excellent technical performance – definitely a rare trait in today’s market.  I really enjoyed using the sleeping bag (how often do you say that about sleeping bags?) and my consistently better sleep spoke volumes to me.  Moreover, it’s a bag that I’m confident taking into challenging conditions with the knowledge that the special design will give me the performance I need with the perks of being able to cook and move around in my sleeping bag.

Buy now: Available from REI.com