Mountain Equipment Kyros Down Jacket Review
The Mountain Equipment Kyros ($600) was built for the demands of high-level alpinism, merging a low weight and minimal packed size with enough warmth and weather protection to handle the windy, sub-freezing conditions of the world’s 6,000-meter peaks. Our tester put it through two months of Colorado winter use—summit pushes up 13,000-foot peaks in negative 10 degree temperatures, ice climbing, winter backpacking, and ski hut trips—and it kept her warm in conditions that had her companions getting frost nip and her soft flask freezing solid in an inner pocket. The wide hood aperture and finicky zipper are genuine frustrations in extreme cold, and it's not a jacket for ultralight objectives. But for high-altitude, high-exposure pursuits where warmth is non-negotiable, the Kyros is one of the most capable jackets we've tested.
Warmth
Weight & Packability
Comfort
Durability
Weather Resistance
Sustainability
Weight
1 lb. 4.1 oz.
Insulation
7.1 oz. of 800-fill down
Fabric
30D
Packable
Yes (stuff sack)
Pros
Cons
Mountain Equipment Kyros
For this season's top puffies, see our guide to the Best Down Jackets.
The Mountain Equipment Kyros is a heavyweight down jacket built for winter alpine climbing or high-altitude mountaineering. With 7.1 ounces of 800-fill down (in the women's size medium), lightweight shell and liner fabrics (30D and 10D, respectively), and a hybrid baffling system that combines conventional stitched-through and pleated baffles, it offers generous insulation and uses it efficiently, resulting in a winning combination for sub-freezing warmth.
The Kyros has kept me warm in truly demanding conditions. On a mid-February mountaineering trip in the Colorado Rockies, I wore it on a summit push up a 13,400-foot peak, where temperatures hovered around -10 degrees Fahrenheit with high wind gusts. My upper body stayed comfortable both on the way up and on the way down—a meaningful feat given that my companions got frost nip on their cheeks and noses, and a soft flask I'd tucked into the inner pocket froze solid. Back at our 12,000-foot camp, I was cozy in the Kyros in calmer 10- to 20-degree conditions. Later in the season, it served as my warmest layer on ski hut trips. All told, it’s earned the reputation as the warmest jacket in my closet, which is especially impressive given how lightweight it feels.
The Kyros’ generous down fill is what contributes most to its insulation, but the jacket also offers a battened-down feel via a tall collar and deep hood. While climbing, the hood securely encased my head and helmet, and I could tuck my face deep into the lofty collar to keep it warm. The collar and hood are generously sized to accommodate a helmet, which is exactly right for its intended use. The tradeoff is that it feels a touch loose in high winds—the collar needs to be fully zipped for the hood to stay in place; otherwise, it has a tendency to fly off. Once cinched down, though, both the hood and collar feel comfortable against the skin and do a solid job sealing out the cold.
My typical layering system underneath the Kyros includes a merino wool base layer, a fleece midlayer (Polartec Alpha is my go-to), and a light puffy. That’s right—I’m putting a puffy under the puffy. This doesn’t mean that the Kyros isn’t warm, but rather should communicate the depths of cold it’s really built for. It is emphatically an outer layer for the coldest, most demanding conditions rather than an everyday jacket. Push it into temperatures above the 30s without wind, and you'll swamp out quickly. But when all my other down jackets fall short on cold, windy winter summits, the Kyros delivers.
The Kyros is not a lightweight jacket, and it doesn't pretend to be. At 1 pound 4.1 ounces for a women's medium, it's noticeably bulkier than slimmer everyday puffies like the Black Diamond Access Down Hoody or Patagonia Down Sweater Hoody (both 12.1 oz.). It’s even significantly heavier than a midweight yet exceptionally lofty jacket like the Patagonia Fitz Roy Down Hoody (14.8 oz.). And while it packs into its own hood and can be compressed further from there, it's never going to disappear into a pack the way an ultralight down layer would.
That said, the Kyros’ weight and bulk need to be understood in context. Compared to a traditional heavyweight parka with comparable warmth—like my old Mountain Hardwear parka—the Kyros’ high-loft down insulation and lightweight shell fabric mean it's significantly more efficient in terms of warmth for the weight. As a result, it’s a great option for high-altitude, high-exposure day hikes and winter backpacking trips where serious warmth is non-negotiable, but where I don’t want to carry a behemoth. For ultralight objectives or three-season use, its weight and bulk are overkill.
For a jacket built to handle the harshest alpine conditions, the Kyros is surprisingly comfortable to wear. The fabric is soft and smooth against the skin inside and out, and I've slept in it on several winter camping nights without any complaints. Its mobility is also impressive for a jacket of this size and warmth level—not as flexible as a light- or midweight layer, but as an outer parka, it moves with you better than you'd expect. I’ve been surprised by how comfortable it is to wear all day during big mountain missions, thanks in large part to its relatively low weight. The Kyros feels noticeably less burdensome than my old synthetic Mountain Hardwear parka, which weighed me down considerably more.
The Kyros has a relatively thin build that prioritizes weight savings, but Mountain Equipment didn’t take it too far. The 30-denier shell has held up well during my rambunctious testing, and the overall construction feels high-quality and function-focused. More than anything, I don’t feel like I’m wearing a delicate paper-thin jacket, which is a breath of fresh air compared to some ultralight down jackets I’ve worn. I’ve had no qualms stuffing the Kyros into my pack and pulling it out up high on peak bagging missions, winter backpacking trips, at the belay while ice climbing, and in the evenings on ski hut trips.
The one frustration worth flagging is the main zipper, which can be finicky when zipping the hood all the way up. One time, in temperatures around -20 degrees Fahrenheit with wind chill, I struggled to get it fully zipped one-handed and had to remove my outer mittens to get the dexterity needed to close it. Suffice it to say, that was a meaningful inconvenience in those conditions.
The Kyros isn't a waterproof jacket, but in the conditions it's designed for, it doesn't need to be. Most of my testing took place during winter in Colorado—temperatures well below freezing with sun, light snow, and high winds ranging from calm to sustained 30 to 50 miles per hour with gusts strong enough to knock me off balance. In all of those scenarios, the Kyros’ shell performed excellently: Its baffle-free construction did a great job keeping wind out, and it shrugged off any snow with ease. Notably, the Drilite Loft shell has water resistance baked in, so you don’t have to maintain it like you would a shell with a DWR finish, which wears off over time. I wasn't able to test the Kyros in rain, which is largely beside the point; for a winter summit push in a blizzard or sustained wind, I'd trust the Kyros without hesitation.
Coverage is excellent too: The back hem is long enough to cover my butt, the collar zips up to the chin, the hood fits over a climbing helmet, and the hem cinches down to seal out drafts. Together, they minimize the amount of exposed skin in conditions where frostbite is a real concern.
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Longevity
Choosing durable outdoor gear is perhaps the most effective way to reduce environmental impact—the longer it lasts, the less it needs to be produced. Our proprietary longevity rating evaluates overall build quality based on factors such as materials, fabric denier, component durability (including zippers and toggles), real-world performance as reported by our field testers, and our experiences with the brand.
Responsible Down Standard
The down used in this product is certified to the Responsible Down Standard (RDS). Set by The Textile Exchange, the RDS is the leading certification for sustainably sourced down in the outdoor industry. It ensures that down suppliers use sustainable land management practices, prioritize animal welfare, and provide workers with safe working conditions and fair wages. Third-party audits are conducted at all stages of the supply chain, starting with the farm supplying the down.
PFAS-Free DWR
This product’s DWR (Durable Water Repellent) finish is made without per- and polyfluoroalkyl substances (PFAS). These synthetic compounds are known as "forever chemicals” because they take an extremely long time to degrade, if at all. PFAS can eventually end up in everything from soil to drinking water and have been linked to a range of health issues.
Recycled Materials
This product is made partly or entirely from recycled materials, the most common being nylon, polyester, wool, and down. Some products include a single recycled component or partially recycled fabric, while others are 100% recycled (generally excluding accessories like zippers, Velcro, toggles, etc). Look for these details in our product sustainability report linked below.
Bluesign Approved
Bluesign Technologies, based in Switzerland, operates a third-party textile certification system that ensures materials are manufactured to strict environmental, chemical, and worker safety standards. A Bluesign-approved material indicates that it has undergone a rigorous vetting process based on the criteria above. A Bluesign Product goes the next mile, containing at least 90% Bluesign-approved fabrics and at least 30% Bluesign-approved accessories.
Responsible Manufacturing
This criterion evaluates this brand's commitment to fair wages, safe working conditions, and reducing its environmental impact throughout the production process. Responsible manufacturing is most commonly demonstrated through certifications and membership in programs such as Fair Trade Certified, Fair Wear Foundation, Worldwide Responsible Accreditation of Production, and the Fair Labor Association. We also recognize brands that prioritize local production, such as those that manufacture primarily in the United States or Europe, to reduce carbon emissions, maintain better oversight of working conditions, and comply with strict social and environmental regulations.
Recycled and/or Reduced Packaging
This brand uses recycled packaging and/or is making efforts to reduce packaging altogether. For example, it may use a certain percentage of recycled cardboard or make efforts to use less plastic across its packaging operation. In some cases, brands also use Forest Stewardship Council-certified paper products, which helps to ensure sustainable sourcing of forest materials.
Repair Services
This brand offers repair services, which can extend this product's lifespan and reduce overall consumption. Some brands offer comprehensive repair programs that can fix a wide range of issues, while others have more limited capabilities. If a brand's warranty policy only covers replacement, rather than repair, these programs usually do not meet this criterion.
Resale and/or Recycling Services
This brand has a resale and/or recycling program, which helps keep gear in circulation for longer and out of landfills. The most common form is a trade-in program, where consumers can exchange items for store credit, which is then resold. Some brands accept products back for recycling at the end of their life, thereby reducing waste. Occasionally, some do both.
Carbon Footprint Tracking
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Annual Impact Report
This brand produces and publishes an annual impact report for public consumption, tracking its environmental footprint and sustainability efforts. These reports vary in form but generally cover topics such as material sourcing, greenhouse gas and emissions tracking, waste and water usage, supply chain analysis, and packaging efforts. An impact report is an important step toward transparency and accountability on the sustainability front.
The Kyros offers a generous pocket layout for a down jacket, and I used every single one of them. There are two external chest pockets, two large hand pockets, and two internal pockets. All four external pockets are large enough to fit a phone or an avalanche beacon, and the internal pockets are roomy enough to fit a one-liter soft flask, gloves, or climbing skins on each side. In practice, I use the hand pockets for gloves and snacks and the internal pockets for water—an important consideration on alpine climbs where stopping to dig through a backpack in extreme cold simply isn't practical.
The hood is large and helmet-compatible, which is exactly what you want in a jacket designed for technical alpine use. My only complaint is that it stays reliably in place only when the jacket is fully zipped. Otherwise, its large aperture has a tendency to fill with gusts and fly off in heavy winds. In my opinion, it's a fixable design issue that would significantly improve the jacket's already impressive cold-weather performance.
Tester: 5'9" 135 lb.; 33" chest, 27" waist
Size tested: Small
I'm typically between a small and medium in jackets and went with a small here, which was the right call. Mountain Equipment designed the Kyros with a regular rather than slim fit to accommodate layers underneath, and the small delivers on that promise: I was able to comfortably fit a base layer, midlayer, and light puffy underneath while maintaining good mobility and warmth. The shoulders are comfortable and non-constricting, and I had full range of motion for scrambling and ice climbing without feeling restricted. The back hem is long enough to cover the seat, and the sleeves extend fully over the wrists—an important detail in extreme cold where any exposed skin is a liability. Importantly, the Kyros doesn't work well as a midlayer: I wasn't able to fit a shell comfortably over the top, so plan to wear it as your outermost layer in the cold and shed it when conditions warm up.
Patagonia Fitz Roy Down Hoody ($399): Tone it Down
If the Kyros feels like more jacket than your objectives demand, the Patagonia Fitz Roy is worth a look. At 14.8 ounces, it's more than 5 ounces lighter, and its hip-length cut is less restrictive and more packable. The tradeoffs are significant, though: the Fitz Roy carries only 4.5 ounces of 800-fill down compared to the Kyros' 7.1 ounces, its thinner 20-denier shell is more vulnerable to wind and abrasion, and its standard baffling leaves stitch holes that the Kyros' hybrid construction eliminates entirely. The Fitz Roy is a capable midweight layer for lower-elevation objectives or more moderate temperatures where you need insulation without bulk—we've worn it extensively for alpine rock climbing in the Fitz Roy Massif. For 6,000-meter peaks and the coldest winter lines, the Kyros is the purpose-built option. For a deeper dive, read our Fitz Roy review.
Rab Neutrino Pro ($450): A More Versatile All-Rounder
The Rab Neutrino Pro is one of the Kyros' closest rivals in this category—both are heavyweight down jackets built for cold alpine environments, but they serve somewhat different ends. The Neutrino Pro is the more approachable, versatile, and affordable of the two, flexing comfortably between general mountaineering, cold belays, and high-output hiking. It still packs a punch with 7.5 ounces of 800-fill down and a 20-denier Pertex Quantum Pro face fabric in a 1-pound 2.3-ounce build—but its stitched-through baffles are less insulation-efficient than the Kyros' box baffle construction, and its fewer pockets could be a dealbreaker for truly technical use. For a versatile, comfortable cold-weather jacket that performs across a wide range of winter pursuits, the Neutrino Pro is an excellent choice. For committing, high-altitude climbs in the harshest conditions, the Kyros is the more capable tool. For more, see our review of the Rab Neutrino Pro.
The Mountain Equipment Kyros is a technical, heavyweight down jacket for serious alpine conditions, built to deliver maximum warmth at a minimal weight when temperatures drop below zero. If your winters involve technical routes, high-exposure objectives, and frigid belays, it earns its place in the pack.
Warmth
Weight & Packability
Comfort
Durability
Weather Resistance
Sustainability
Named after one our our favorite mountains, the Fitz Roy is a soft and cozy mid-to-heavyweight jacket that offers efficient warmth for sub-freezing conditions. However, it lacks a few key features we look for in a belay jacket, including a long hem, two-way front zipper, and sufficiently wind and water-resistant face fabric.
Warmth
Weight & Packability
Comfort
Durability
Weather Resistance
Sustainability
A winter-weight down parka that can handle light moisture thanks to a very weather-resistant Pertex Quantum Pro shell and hydrophobic down fill. We love this jacket for ice climbing, cold-weather cragging, and ascending some of the Lower 48’s tallest peaks.
Warmth
Weight & Packability
Comfort
Durability
Weather Resistance
Sustainability
Is the Kyros for You?
The Mountain Equipment Kyros is a heavyweight technical down jacket, built to maximize warmth and minimize weight for demanding pursuits in sub-freezing conditions. If you've found yourself on a cold, windy summit or at a frigid belay, wishing you had brought something warmer—or if you regularly pursue objectives at altitude where the consequences of being underdressed are real—this is the jacket that fills that gap. It's purpose-built for the kind of cold that most jackets can't handle. It's too warm and bulky for high-output activities and three-season use, but if your winters involve alpine starts, technical routes, and temperatures that test the limits of your gear, the Kyros earns its place in the pack.
Go for it if you pursue alpine objectives in extreme cold and need a jacket that delivers serious warmth and wind resistance without weighing you down.
Pass on it if you're looking for versatile midweight warmth or a casual everyday or ski jacket.
stay warm out there
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