Atom

With a comfort rating of +40 degrees Fahrenheit, this 1-pound bag is made for summer nights.

One of the lightest 40-degree sleeping bags you can buy, the Atom is the cousin to the 30-degree Helium we reviewed in the March issue. Marmot touts the Atom as a 16-ounce bag, though our sample weighed in at 18.5 ounces – still a 5-ounce savings over the Helium. Like the Helium, the Atom keeps its weight down by using ultra-high-loft 850-fill down, a Pertex Quantum Ripstop shell, and a half-length zipper (this same architecture is also used by a few smaller manufacturers to produce bags of similar weight). The 850-fill down is luxurious and an easy-access drawcord cinches the hood down snugly around your head on cold nights. I found the temperature rating to be accurate, though if you don long underwear and, say, a down vest, the bag could serve you well in conditions much colder. The Quantum fabric is outstanding – it’s soft, downproof, and supremely packable. For its weight the fabric is surprisingly durable, though probably not as durable as bags that weigh twice as much. But, hey, the Atom can pack down to the size of a large grapefruit, which is worth a lot when you’re traveling svelte.

Comfortable nights in near-freezing alpine camps in Washington’s Glacier Peak Wilderness convinced one tester that this 850-fill-power, 40 degree F bag was “impressively warm for such a featherweight.” On an 11-day expedition through Alaska’s Revelation Mountains, our Rocky Mountain editor watched a companion stuff his Atom down to the size of a large coffee mug – after sleeping snugly in 30s temps – while the rest of the group hauled 3-pound synthetics. Add a comfortable cut and well-contoured hood design.

This 850-fill-goose-down bag is rated for temps down to 40 degrees, but testers stayed toasty warm even when the mercury was in the 30s. The billowy hood muff blocks out drafts around the shoulders and taffeta lining makes you feel like you’re sleeping between silk sheets. However, for those who value a little space to squirm, the mummy-shaped Atom can feel constricted around the legs. A stiff zipper guard stays in place to block out drafts no matter how much you move around and sewn-through baffles keep the down evenly distributed.

Feel that copy of HOOP in your hands? It’s about the same weight as Marmot’s Atom sleeping bag. Packable to the size of a mini-basketball, what the Atom lacks in size and weight, it makes up for in performance. The certified 800-plus fill goose down and 3D hood that encases your head keeps things toasty when the nighttime temperatures dip (this one is rated for 40 degrees Fahrenheit).

Marmot Ultralight Down Bags
Sleep-anywhere evidence that luxury and lightweight can go hand in hand.

Want to see a down bag puff up like a hot-air balloon? Unfurl one of these 850-fill sacks and stand back. Each bag in this line is overstuffed with the highest quality feathers we’ve seen – light, compressible, and amazingly lofty. And the down is well distributed throughout – with enough on the bottom to keep your back from chilling if you roll over. The no-skimp approach to down has made these bags a tester favorite since 2001. Add Pertex Quantum shell fabric – which is breathable, wispy, water-resistant, and durable – and simple designs that are comfortable but thermally efficient, and you get standard-setting bags. If you require separate pockets for your iPod, make-up kit, and dental whitening strips, or other doodads like foot vents and pad straps, these elegant sacks are not for you. But what features there are we love: A muff around the face seals well without forcing you to crank down the drawstrings; the footbox is roomy enough for booties and hot-water bottles; and zippers stay zipped without relying on scratchy Velcro. Plus, there’s a version for virtually every trip.