Gear Box: Sierra Designs Flex Down Jacket


While going through the process of selecting gear for my recent Everest Base Camp trek, I began to notice that a common theme was emerging. It was clear to me that no matter what new items I added to my pack, they each shared a few common elements. Each was light in weight, compact in size, and seemed to serve its purpose very well. Each of those elements is very important when you’re hoping to travel lightly and efficiently.

That description can definitely be applied to the Flex Down Jacket from Sierra Designs, which I carried with me as a last defense against the cold air and biting winds of the High Himalaya. My plan was a simple, and common one, carry a light and heavy fleece for use as the altitude warranted, then pair one or the other with the Flex Jacket on approach to base camp as needed. As it turned out, the Flex was plenty warm on it its own and I never needed to wear more than a base layer underneath it.

My first impression of the Flex came days before I would ever wear it in the Khumbu. The night before I set out on the trip I was busy organizing and packing all of my gear when it came time to pack the jacket, which I feared would take up far too much space in backpack.

But fortunately, the Flex compresses down quite nicely, and when folded properly, it takes up a surprisingly small amount of space for a 750-weight goose down jacket. In the days ahead, that would prove to be a valuable asset, as I wouldn’t wear it until the high point of the trek when we were on our final approach to Base Camp.

When the need did arise for me to don the jacket at last, I found other reasons to be further impressed. The Flex proved to be incredibly warm and wind proof, and while I was only going as high as 17,600 feet, I couldn’t help but think that I’d stay warm and comfortable much higher on the mountain, and under a range of weather conditions.

The jacket fit well, but wasn’t restrictive in any way, allowing me to hike through challenging conditions without feeling it was a hindrance of any kind. The puffy layering, coupled with the elastic seaming, protected me from the elements, without a hint of cold air getting inside.

The Flex doesn’t skimp on the features, and Sierra Designs has gone all out to make sure we stay comfortable in a variety of situations. For instance, the jacket has a warm, insulated hood and two fleece lined, zippered pockets for your hands. Internally there is a pair of large mesh pockets that are perfect for keeping items that you might need close at hand, such as a pair of gloves or water bottle.

Sierra Design has done a great job, top to bottom, with this jacket. Aside from all of the things I’ve already raved about, I was also very impressed with the overall design and build quality of the Flex. After having it smashed flat at the bottom of my pack for days, it not only expanded back to its original shape quite nicely, it did so without the hint of a single feather escaping from the inside.

The Flex is a versatile, well-designed jacket that will serve you well in a variety of situations. Whether you’re headed out on a high alpine climb, hitting the slopes, or just wandering around town (a very, very cold town!), you’ll stay warm and comfortable. You might look a bit like the Stay Puft Marshmallow man, but you’ll definitely be warm.

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3 thoughts on “Gear Box: Sierra Designs Flex Down Jacket”

  1. Thanks so much for your review- after hearing what you are planning on doing with the down jacket I am sure that the jacket will also serve its purpose for what I need it- walking around in the city during winter time.
    Thanks again and good luck for your trek!

  2. Long time Sierra Designs fan, and love the flex jacket, but: No cinch cord at bottom, just elastic and no 2 way zipper, and kind of useless (small) cell phone pocket inside of hand pocket making pocket slightly less comfy. Still a great jacket, but could have easily been killer.

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