Review: Mountain Hardwear Phantom 0 Sleeping Bag

Winter Sleeping Bag
Mountain Hardwear Phantom 0
$680, 2 lbs. 9 oz./1162g (regular, 72-inch)
Sizes: short, regular, long

The forecast made me sit up and wonder: Will my bag be warm enough? For the three nights in late December that I planned to spend in a tent in Idaho’s Boise Mountains, lows would drop into the teens and single digits Fahrenheit—slipping below the “comfort” rating and approaching the “limit” rating of my Mountain Hardwear Phantom 0. And this on my maiden voyage with the bag; I had not used it yet. As it turned out, I had nothing to worry about with this extraordinarily warm and packable, ultralight winter sleeping bag.

I found the Phantom 0 impressively warm even on a night that plunged to 3° F—10 degrees below its EN comfort rating of 13F/-11C and near its 0F/-18C limit rating. And yet, I slumbered comfortably wearing only midweight top and bottom layers and warm socks, adding a wool hat only during the night. I have long observed, as a warm sleeper rather than a cold sleeper, that only the highest-quality down bags will keep me warm down to their temp rating. (I didn’t have nights in this bag anywhere near the Phantom 0’s bone marrow-thickening extreme rating of -38F/-39C.)

One defining metric tells much of the Phantom 0’s story: A bountiful 30 ounces of 850-fill-power goose down constitutes three-fourths of the bag’s total weight. Stuffed fat with nearly the highest-quality down on the market (there are a few bag models with down rated at 900-fill) explains this bag’s two major advantages: a sky-high warmth-to-weight ratio and excellent packability.(The down quality also partly explains the price.) Even after being compressed for hours, this fat bag lofts up quickly.

Not only does the Phantom 0 have a greater fill weight and lower total weight than many bags in this temperature-rating category, but at about 2.5 pounds, it weighs no more than many 600-fill down bags that carry an EN limit rating of 20F. Plus, it packs down to 8.25 ins./21cm x 16.5 ins./42cm. Sold with a compression stuff sack included (3.5 oz.), the Phantom 0 compresses as compactly as some 20-degree down and synthetic bags. It bears noting the obvious point that I’m drawing comparisons between the Phantom 0 and bags that are in an entirely different class for warmth.

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Mountain Hardwear Phantom 0 sleeping bag.
Mountain Hardwear Phantom 0 sleeping bag.

As anyone who has carried a heavy and bulky bag (something I have done) knows from experience, weight and bulk are a big deal when you’re talking about a winter bag. Any attempt at keeping a multi-day pack manageably lightweight in winter goes out the window if your bag’s weight soars toward four pounds and, when stuffed, it occupies a disproportionate share of your pack’s volume.

Other features making this a very warm bag include a fat draft collar and face gasket and a draft tube inside the zipper to efficiently trap heat; a mummy cut for efficiency trapping heat; and a four-chamber hood, which keeps the insulation from migrating, creating cold spots. I found the hood adjusts easily to form a close fit around my face and can be closed up to a small breathing hole on really cold nights.

Apropos for a winter bag, this mummy has good space inside for fitting extra clothing at your feet (to boost insulation around the part of your body that can get cold quickly), with an 86-inch length—but just as important, respectable space around your torso, with a relatively roomy 58 inches of girth at the shoulders and 52 inches at the hips (all measurements for the size regular bag). I stuffed a very warm down jacket, unzipped and open, inside the bag with me and never felt too cramped—but that comfort may vary between individuals (I’m 5’8’’, 155 pounds, with a 38-inch chest and 30-inch waist).

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Mountain Hardwear Phantom 0 sleeping bag.
Mountain Hardwear Phantom 0 sleeping bag foot box.

The contoured footbox also has space to pack some extra layers around feet—and allows your feet to assume a natural position when sleeping. The two-way zipper enables ventilating from either end—although I’ll never have to ventilate my feet in winter, I suppose some people might—and its zipper pull glows in the dark.

The DWR-treated, 10-denier nylon Ghost ripstop shell fabric contributes to making the bag more compressible but is at the lighter end of bag fabrics, so take care not to let it contact any sharp objects. The lining is made with recycled, 20-denier nylon taffeta.

Other Phantom versions include the highly water-resistant Phantom 0 Gore-Tex Windstopper shell ($760, 3 lbs. 7 oz., regular), the Phantom 15 ($520, 2 lbs., regular), and the Phantom 30 ($420, 1 lb. 5 oz., regular).

A tip: Get the Gore-Tex shell only if you plan to sleep without a shelter and may get snowed on. A Windstopper shell will keep much of that external moisture out of the bag’s insulation; but if you’re in a tent, most of the moisture penetrating the insulation is likely to come from your body, and you’re better off with the standard ripstop shell, which will allow that body moisture to exit the bag more quickly than Windstopper.

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Mountain Hardwear Phantom 0

Warmth for its Weight
Warmth When Wet

The Verdict

Among the warmest and most packable ultralight sleeping bags in its temperature rating, with comfortable space inside and a nice hood and other features, the Mountain Hardwear Phantom 0 ranks among the very best bags for winter backpackers or campers, mountaineers, and people on chilly, three-season trips who need extra warmth even on nights that won’t approach the Phantom’s comfort or limit ratings.



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See all of my reviews of sleeping bags that I like and all of my reviews of backpacking gear, and my articles “Pro Tips for Buying Sleeping Bags” and “10 Pro Tips: Staying Warm in a Sleeping Bag.”

Whether you’re a beginner or seasoned backpacker, you’ll learn new tricks for making all of your trips go better in my “12 Expert Tips for Planning a Backpacking Trip,” A Practical Guide to Lightweight and Ultralight Backpacking,” and “How to Know How Hard a Hike Will Be.” With a paid subscription to The Big Outside, you can read all of those three stories for free; if you don’t have a subscription, you can download the e-guide versions of “12 Expert Tips for Planning a Backpacking Trip,” the lightweight and ultralight backpacking guide, and “How to Know How Hard a Hike Will Be.”

NOTE: I tested gear for Backpacker magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See The Big Outside’s Gear Reviews page for categorized menus of gear reviews and expert buying tips.

—Michael Lanza

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