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Smartwool Mountaineering Extra Heavy Crew Socks

rated 3 of 5 stars
photo: Smartwool Mountaineering Extra Heavy Crew Socks hiking/backpacking sock

Outstanding comfort and function, to protect my most critical of trail gear -- those size 12 feet! Makes a great stocking stuffer anytime of the year ... it's the sock that I like getting stuffed into most! If foot comfort is important to you, this is a must try sock.

(Durability looks great so far for me and in other online reviews. I need another minimum 30 more hikes before I can better judge durability. I'll adjust rating accordingly when I am 100% sure of durability.)


  • Exceptional compressible loft and softness without feeling bulky
  • Goose down like huge temperature comfort range, magically feeling warm on cool days and not hot on warm days!
  • Lofty curly fibers allow awesome air circulation, breathes well and does not feel "muggy"
  • Wicks, sheds and reacts to water very well, as gets wet does not feel water soaked
  • In spite of thickness does not feel bulky or constrictive within my boots


  • More expensive than some other popular options e.g., REI Expedition
  • Red color foot area makes it hard to tell if you are bleeding ... just kidding, the point of these is to prevent damage to feet

-- Titles have changed a little for the sock.  I purchased "Mountaineering Extra Heavy Cushion".  I think it is the same as "Mountaineering Extra Heavy Crew". --

Sock Description by Smartwool for "Mountaineering Extra Heavy Crew"

Made just for high-altitude, low-temperature excursions, the Mountaineering Extra Heavy Crew sock by Smartwool is the top choice for mountaineering, ice climbing, or peak bagging in the snow. PRODUCT FEATURES: Extra heavy, full cushioning all around your foot Superior moisture control and ventilation regulates your foot temperature to keep you comfortable in the harshest conditions Reinforced arch provides support and keeps the sock in place all day Materials: 83% Merino Wool, 16% Nylon, 1% Elastic

The Review

Why would anyone want a warm cushy comfortable sock anyway? 

The photo above is a deluxe snow cafe like location is the cushy-ist part of a typical group snowshoe trek (last year to Artist Point, Mt Baker -- I'm in the rust brown Marmot fleece hoody, as nearly part of that deadwood). It's nicer, and even more enjoyable, when one's feet are not cold and killing them, from their sock choice. (Future review hint:  look closely at everyone's feet, MxxR snowshoes RULE out here, in our dense, re-frozen icy snow climate ... oh yes steep hills and rocks too..  Why are my snowshoes metal (not mellow) yellow? Wait for the review to see.)

What to look for to get the right sock, there are so many brands and styles at those big box stores!


Lable disclosure of fabric types


I have other Smartwool socks, and try as I may, so far they often are not my "go to" socks. Their mounteering sock feels to be in a fully different class! These are much softer, less restrictive, feeling less hot ... but still winter warm quality.


Closeup view shows why the sock feeling like walking on clouds ... the curly loops of soft fibers look like a collection of little clouds, floating in and mostly consisting of air. The structure is not bubbles, but open spaces where the air can circulate and not trap heat or moisture. And these are much better than walking on clouds ... they are right there in your boots, so you don't fall through.


I understand why they wanted shading to hide boot staining and, dare I say, add some style to hide in my boots. Is the red to hint at medical grade protection or to have some joy in shocking others with what might look like bloody stumps emerging?  Or is it to hide the bloody result of wearing them?  

I'm at a loss explaining this, because of all the trails socks I've used over the years, these feel the least capable of hurting me. I actually went in the day I got them to buy Darn Tough socks, because a much trusted hiker friend raves about them. I couldn't find a well cushioned Darn Tough. And I'm sorry, but they felt 'Darn Rough' to me for aggressive rocky and other mountaineering like uses.

The extended crew height of the socks is enough to protect me in my mountaineering boots. The elastic top is pilable enough to make it easy to get the socks on. The marked sock softness hides seams, which are minimal anyway.  The socks are tube like and can be rolled on if your feet get wet/sticky after wading.

I roll ...


What's not to like about these highly functional socks?  I love mine, more than any other sock I have gotten yet. I could have purchased a Large, instead of Extra Large. But this choice allows layering when I want to get crazy thick for mountain snowshoeing. And it makes it less likely to grab my socks, if she packs her backpack first ... the best gear has a curious way of hiking out on others.

OK, about time for the rubber to hit the road ... then trails.

It's quite early Saturday AM (4:13 AM) and I'm up final sorting out for two day hikes for this weekend! The mountaineering sock shown will be at the foot foundation for both. Tucked into my old Asolo Power Matic 200 boots, the long crew legs can be lengthened or rolled over depending on where i want padding, extra localized warmth, upper boot block for debris, or upper boot lace cover to keep cleaner lace area. This weekend heavy rains and marked winds are predicted. So I'll use the small Outdoor Research low gaiters, kept tidy with that green rubber band. The gaiters will help keep the socks, upper boots, pant bottoms AND me clean.

This is a sock review, so why do I mention so much other gear? In outdoor activities you have to take a practical systems approach to select and carry the right gear for the intended use. And it should all work well together. At a minimum your comfort thus enjoyment is at risk. If you are in the outback away from help, try then your safety, and potentially life, are also considerations.

Too much talk ... about time for some action!


The socks' insulating ability, combined with goose down like comfort range, will keep my ankles and lower legs toasty warm, so that the muscles/tendons stay warm and pliable (if mine get cold for extended periods when hiking, they can otherwise feel stiff and tight over time). The wickability and breathability of the soaks, pants, boots and gaiters will manage moisture.  

If I layer too warm and they soak out I have backup socks that I can change into during a break. Since it would be a warmth issue then, these are the standard (thus less insulative) standard Smartwool hiking crew sock.  I have a couple other tricks to manage heat and aeration here. If not raining, gaiters can come off. If I still need cooling, a zipper on my gusseted Outdoor Research Cirque Pants can turn them into a bell bottom. And if I need open legs, but a gaiter like effect, the Cirque cuffs have grommets so that a cord can be used to make the cuffs into a gaiter, with bell open or not.  

This all sounds complicated, but it is not. All adjustments can, and will be made on the fly, as I hike to get pinpoint accuracy in adjusting desired comfort and function. A huge part of what makes this work, is the design of that foundation sock.

Second hike will be Heather Lake ... this is last year about this time with my daughter. Microspikes will be with me just in case.


Source: bought it new
Price Paid: $23 minus 20%, REI sale. Was suggested to me over their own Expedition sock!

Thick merino wool sock for the coldest weather. Warm, comfortable, wicks well. High volume, make sure they fit in your boots. If they get very damp, prone to stretching out (but will rebound next washing).


  • Warm
  • Wicks well
  • Comfortable


  • Can stretch out

My favorite winter hiking/camping sock for several years. Thicker and warmer than anything else I have been able to find (caveat—i'm testing a pair of Bridgedale Summit socks that are pretty close). Bcause the sock is so thick, i can't wear them with any of my non-winter hiking boots. They are reserved for the really cold days snowshoeing in Pac Boots or the winter mountaineering boots. paired with good boots, my feet have been toasty in these socks at thirty below zero, Fahrenheit, and they would have been happy at much colder temps.

20190114_212636.jpgAbove, you can see the socks rolled down. The big loops inside help wick moisture away from your feet.  

20190114_212649.jpgThis is a fairly high sock, to near the top of my calf.  


Side view: the bottom is slightly more densely woven than the rest of the sock.  

Durability has been excellent, though note that I don't use them much in the Mid-Atlantic, they're mostly for trips up north. Only hole was inflicted by a moth on one sock. They have worn very well. They are somewhat pilled on the exterior after nine or ten years. That's cosmetic and hasn't affected the fit or performance; the loops inside the sock have worn very well. On longer trips, the socks tend to become a little stretched out, though not so much so that it has been a problem. They rebound next time you wash them.  

I only run these in the clothes dryer for a few minutes, then line dry them to avoid shrinkage over the long term. Washing them inside out can help with pilling but won't remove any debris or dirt from the exterior. I have also noticed that the clothes dryer tends to make the fuzzy interior bunch up somewhat over time.

A winner. Pricey, but...having ten toes is priceless.


Several years, used primarily for hiking/climbing in double plastic boots or snowshoeing in insulated Merrell boots. Occasionally in a pair of LL Bean boots for walking the dog on cold days.

Materials: merino wool blend
Use: winter mountaineering/snowshoeing
Break-in Period: none
Weight: not much
Source: bought it new
Price Paid: $18

Smartwool Mountaineer Socks: Thick, warm, comfortable

Best Use: Ice and mixed climbing, winter backpacking, mountaineering and alpine hiking
Sock Height: Crew
Cushioning: Heavy


  • Sizing clearly indicated on the sock
  • Elasticized arch and ankle support designed to keep the sock in place
  • Made in USA


  • Wicked expensive
  • Almost never on sale

Product Specifications:

  • Fabric Details: 74% Merino Wool, 25% Nylon, 1% Elastane
  • Gender: Unisex


Five years of winter backpacking, winter camping, and snowshoeing — these socks are warm. I have NO BLISTERS when wearing these with a wide variety of footwear including: White Mickey mMouse boots, Sorels, Kamiks, Merells, Koflach Ultras, Timberland, Hoffmans, Georgia Pac boots and now I will wear them with Alico New Guide mountaineering boots.


I have hiked in summer with these. They wick sweat OK.

They are really good when the temperature gets below freezing.


They don't wear out, Washing machine + dryer = no shrinkage. Don't pull out any threads hanging out of your old socks, just take a lighter and melt the thread.

How to Use Them

I bring a minimum of two pairs along anytime I go out snowshoeing and I keep a third pair inside my sleeping bag when it gets wicked cold whilst winter camping.


LG stands for Large. See the photo.

I wear 8.5 size shoes which is the end of the Smartwool Medum size.

I wear these LG socks over a liner sock because I don't want them too tight.

Source: bought it new
Price Paid: $17.98 & free shipping

Very good. I love good socks and feet are so important to safety and success of adventure and competition.

Warm, thick padding, smooth and comfortable but not too hot as they vent well and with good temperature control. As well they move moisture well too. I use a liner sock under them when using in excessive movement conditions and this makes nice benefit and safety against any possibility of blisters if even that could happen.

At the end of a day when they may be needing a wash / rinse this is easily done and with a gentle ringing out of the water they also dry well, e.g. overnight.

If any change I would like them to be up to 5 inches longer.

Yes, I do recommend and would buy again from REI.

Price Paid: $22.95

SmartWool hiking socks are some of the most expensive socks in the market. I have no problems paying more for a piece of gear that will out perform less expensive items of similar purpose, however it is not the case of SmartWool socks that they are worth their price.

Smartwool socks wear out so fast it's ridiculous - you could buy socks from a cheap department store and those would last longer. While it may be true that SmartWool has some attractive, comfortable designs, so do some other companies.

My advice is that you try a WigWam sock because they are less expensive, just as attractive and comfortable, and it is not possible for a sock to wear out faster than SmartWool.

Price Paid: $18

Proper socks for cold weather activities.


  • Insulation
  • Comfort


  • Lose elasticity in time

They offer good insulation and comfort. In case of very low temperatures, a very thin liner can be used.

They are bulky so make sure they fit in your boots without restricting your blood circulation.

The only complaint is they really get loose after some usage, but that's a natural feature of wool.

Source: bought it new

I purchased two pairs, which is bad because they don't even stay up. They bunch down in my boots and start to cause hot spots. I am going to send them to Smartwool and see what they will do.

I have big soccer calves too, by the way, but they need to be taller and a little more snug. Maybe my calves stretched them or are they meant just for very slim built people.

Price Paid: $19/pair

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