User Review: Marmot Men's Helium
Fill: 850 down
Temperature Rating: 15F
Price Paid: $270
This is just a "first impression" of the Helium as I am returning it unused. This is a 2008 model, full zip. I find the "snag free" zipper and draft tube interface unsuitable. The zipper backing is too stiff and the tube too small. Though only a few reviewers have found this a source of cold spots I judged it to be inadequate and didn't want to stuck with an nonreturnable bag.
Other than that it seems to be a well made bag and the breathability of the shell material was superb. IMO, treated waterproof/resistant shells trap body moisture and make for poor down performance. In fact, I have a Sierra Designs 800-fill Trade Wind 15 with the so-called Dri-Zone that is worthless below ~27F. Also my opinion is that "snag free" zippers and waterproof coating are nothing more than marketing strategy or solutions in search of a problem.
I still have my old down California-sewn Trail Wise from 35 years ago and an Eddie Bauer expedition bag from nearly 40 years ago, both are untreated nylon taffeta (also an old Blue Kazoo).
Marmot needs to get back to basics and definitely improve the draft tube design. I live and hike in New Mexico with many side trips to CO, UT and AZ. Spring/Fall high country temps ~15F at night, very low humidity.