Ultralight sleeping bags weigh almost nothing, pack down smaller than a water bottle, and one can easily last for the rest of your backpacking life. Yes, it’s an expensive investment but its longevity, comfort, and incredible stuffability make it much easier to rationalize—especially if you’re the type who expects to be out in the wilds as long as your legs will carry you.
For maximum versatility, I recommend looking for a down bag that will keep you warm in cool to cold, near-freezing conditions. While I’m still sleeping snug in the Mountainsmith Ghost sleeping bag I acquired nearly 15 years ago, I still keep an eye on the latest drool-worthy options in the field—especially since nearly all of today’s ultralight bags now feature water-resistant down, a nice upgrade.
Note that all listed weights and prices are for men’s regular length (add roughly 2 to 4 ounces and $20 to $40 for long versions) and that temperature ratings refer to the lower limit of the industry-standard EN rating system.
Sea-to-Summit Spark Series
This featherweight line of sleeping bags features three versions: the Sp III is the warmest of the bunch (+25 degrees, 22 ounces, $439). Also available is the Sp II (+35 degrees, 16 ounces, $359) and Sp I (+46 degrees, 12 ounces, $299). An unusually short, one-third length zipper keeps the weight down but also limits your ability to keep cool in warmer conditions. Also, like many other ultralight bags, the Spark series also runs narrow (57-inch shoulder girth) and would not be the best choice for broad individuals.
Marmot Plasma Series
This is my dream bag. It does come in at a rather frightening price point, but it also comes as close to ultralight perfection as any I’ve found. A full-length zipper provides full versatility, vertical baffles keep the down from shifting, and a wrap-around hood snugly envelops your noggin. The Plasma 15 is the warmest of the bunch (+18 degrees, 32 ounces, $679); the Plasma 30 is its lighter cousin (+32 degrees, 24 ounces, $579).
Western Mountaineering MegaLite
This is one of the roomiest ultralight options out there—the 64-inch shoulder girth provides ample space for folks who like a little extra room to shift around or to accommodate broad shoulders. And, like all of Western Mountaineering’s bags, the MegaLite is made in the USA (+30 degrees, 24 ounces, $460).