Love this bag. Keeps me warm. For night after night use, this dries quickly in the sun. I just throw it in the bottom of my pack loose. I don't need the extra weight or pain of a stuff sack. Great essential piece of gear. It's the most money I've ever spent on a piece of equipment.

The Helium was the first Marmot bag I bought, but not the last. I was so impressed with it that I rounded out my bag arsenal with the Atom for summer work and the Col EQ for extreme cold applications. Nobody does sleeping bags better than Marmot in my opinion, well worth the investment. Helium is VERY warm, I find its 15-degree rating conservative (but I do sleep warm). Great features, top-quality workmanship, best materials available. Compresses down to a ridiculously small size, lofts back up in no time, the Pertex Quantum shell sheds light moisture without a problem and dries fast. The weight is unbelievable; my Long weighs precisely 2.23 lbs in a small compression stuff sack. People often complain about the stuff sacks Marmot includes with their bags. They are a bit average; a good-quality compression stuff sack is my preferred method, easier on the hands and the bag.

This bag offers an outstanding ratio of warmth to weight, with high-quality construction and materials throughout. The only drawback I've found is that the shell is only mildly water resistant, so for wet climates buy the more waterproof version or take along a BD Winter Bivy (or buy a synthetic bag instead).

This sleeping bag is a great, warm, and lightweight bag. It stuffs down to almost nothing (about the size of a loaf of bread). The 850 down stays fluffy even after being stuffed over an extended period of time. The short zipper is long enough and helps save weight. It was warm down to 30F. (I'm a cold sleeper.) The only disappointment is the stuff sack supplied my Marmot. Marmot makes such great bags but their stuff sacks do not live up to the Marmot name. I bought a good quality compression sack for this great bag!

The Helium Sleeping Bag is a great lightweight sleeping bag. It was warm at 20F. It packs really small; down to bread loaf size. Its short zipper is plenty long enough and helps cut down on weight. It offers enough room inside and the hood and draft collar are comfortable. The loft is great. The 900-weight down is worth the price. Its insulation qualities are flawless. It is a wee bit difficult to stuff in the sack Marmot includes. I will upgrade to a better quality compression sack, but this is a very minor criticism. Marmot needs to include a better quality stuff sack for their great bags.

This bag is the most fluffly, snuggly, warm and light sleeping bag ever! The zipper worked well and never snagged. Stuffed in the bottom of my pack without a problem and was great for some zzzzzzs in the Olympics.

2lbs and it keeps me warm at 15 degrees. It performs just as well as everyone claims. I love this bag, has a nice snug fit, great draw string and packs down to the size of a nalgene practically. The down takes a bit to get fully fluffed, longer then others I have seen and I wish I had the EQ version for more waterproofing. But I would recommend this bag highly.

what can i say? it kept me very warm, i felt snug as a bug camping in winter, in high altitude. the weather was cold enough that there was some snow here and there, to give you a sense of how warm it was. i'm so in love with it that i've used it even when i didn't need it, such as in motel rooms. it's soft, the half zipper works well. when i scrunch it up around my face, there are no scratchy spots. it seemed to resist the slight condensation in the tent. it's not waterproof, per se, but even with a few beads of water on it, it felt dry to the touch. the blue color is awfully pretty, too. did i mention it squooshes down to nothing and weighs even less? it has made backpacking a joy.

So I’m a convert from synthetic, and I couldn't be happier. I could go on and on about the many reasons why natural is better, so I will just list the main points that have been confirmed from the switch. Broader comfort range, fewer cold spots, more compressible and lighter. Spent some nights in the high 20s in this thing. I am greatly impressed and my expectations are exceeded. I am 5.7 and 140, and the regular fits great, with room to move around inside it doesn't feel like I’m too confined or that it's too spacious. This bag will make a perfect winter touring bag where with a bivy or makeshift shelter it won't get much below 30 degrees. I am a pretty warm sleeper I might add so if you get cold easy I would suggest getting something a little warmer.

Nice sleeping bag, but plan on spending an extra $ to buy a compression stuff bag. The bag that comes with it is too small. Marmot not responsive to previous negative reviews of stuff bag and to this buyer's phone call.