Compressibility
The 20-denier ripstop Pertex shell and a soft 30-denier nylon liner, the Helium has some heft. Even with the high loft 850-fill down, the bag doesn’t compress as small as some (such as the Montbell).

Warmth to Weight
Though very comfortable and roomy, the Helium proved remarkably warm, even in the wet-cold camps on of Washington’s rainforests, when temperatures dropped into 20s overnight. With a generous cut, the Helium risked being drafty or holding cold pockets, but our team found this not to be the case. The cut provided just enough room to shift and move without excessive voids to act as cold sinks. The weight of the bag skewed the ratio a bit, however, as the Helium fell solidly into the middle of the weight range in this class.

Comfort
Here’s where the Helium floats above the rest. Whether used by our skinniest hiker or our broadest, the Helium was deemed incredibly comfortable. In addition to a generous taper, the Helium incorporates stretchy materials in the down baffles to help keep the insulation well distributed to prevent cold spots. As a side sleeper, I found I could easily shift from my back to my side, pull my knees upward, and not feel constricted at all. The hood also proved to be one of the more comfortable we used. When loosened it opened enough not to be a bother, but when cinched, it stayed in place and moved with me during the night.

Durability
The ripstop Pertex shell resist snags and seemed impervious to normal wear in gritty camps. We did occasionally catch the shell in the zipper when fumbling for a quick escape (bursting bladders prompt reckless haste) but that never yielded a tear or puncture.

Value
Staying with the pack at the top of the price range, the Helium excels in some categories but comes up a little short in others. For those who favor comfort in camp over less weight (and volume) in your pack, this is a bag worth considering.