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Artilect Boulder 125 Review

A seriously tuned ultralight pair of wool/nylon blend leggings built for fast and light outdoor adventures
artilect boulder 125 long underwear review
The only spandex you'll find in this pair of long underwear is on the waistband.
Credit: Justin Simoni
Top Pick Award
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Price:  $110 List | $110.00 at REI
Pros:  Extremely breathable, ultralight stretchy nylon/Merino wool blend
Cons:  Price may make you do a double-take, care instructions need to be followed when drying
Manufacturer:   Artilect
By Justin Simoni ⋅ Review Editor  ⋅  Dec 2, 2022
Our Editors independently research, test, and rate the best products. We only make money if you purchase a product through our links, and we never accept free products from manufacturers. Learn more
74
OVERALL
SCORE


RANKED
#2 of 12
  • Warmth - 25% 5.0
  • Breathability - 20% 10.0
  • Comfort and Fit - 20% 8.0
  • Durability - 15% 6.0
  • Drying Speed - 10% 8.0
  • Layering Ability - 10% 8.0

Our Verdict

The soft and breathable Artilect Boulder 125 leggings will keep you warm and comfortable, all while being one of the lightest pairs of long underwear we've ever tested. Using an 85% Merino wool/15% nylon Nuyarn blend helps shed that extra weight while being tough enough for your next shoulder season or summer outdoor adventure. Thoughtful design considerations, such as a perforated gusseted crotch area and lower back panels, help create a good fit and maintain great thermoregulation while you're on the move. The sheer fabric dries out quickly and is impressively breathable. Overall, if you can afford this pair, you won't be disappointed.

Editor's Note: This review was updated on December 2, 2022, to add in new testing metrics and more helpful recommendations.

Compare to Similar Products

 
artilect boulder 125 long underwear review
Awards Top Pick Award Editors' Choice Award Best Buy Award Top Pick Award Best Buy Award 
Price $110 List
$110.00 at REI
$110 List
$110.00 at REI
$55 List
$54.95 at REI
$115 List
Check Price at REI
$60 List
$59.99 at Amazon
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Pros Extremely breathable, ultralight stretchy nylon/Merino wool blendA nice balance of warmth and breathability, super cozy, nicely articulated designTough synthetic fabric, four-way stretch for great range of motion, excellent performance for the priceShorter length reduces bunching near ankles, seamless panels provide additional articulation and ventilation only where needed, high waist and thick waistband keeps bottoms in placeAffordable intro to Merino, warm and cozy, wide spectrum of available sizes
Cons Price may make you do a double-take, care instructions need to be followed when dryingExpensive, stretches out in between washes, slow to dry when saturatedHeavier than wool bottoms for their warmthNo-fly design could be inconvenient underneath other layers, fit may be too tight for some body types, priceyStarts off slightly itchy, simplified construction may not be as comfy, Merino wool is delicate
Bottom Line A seriously tuned ultralight pair of wool/nylon blend leggings built for fast and light outdoor adventuresDesigned to keep you warm in the coldest conditions, this is a versatile pair of Merino wool bottomsA great synthetic thermal long underwear at an unbeatable price for the warmth and durability they provideCarefully engineered 3/4 length thermals with compression pants-like tightness that’ll keep you warm and super comfortable while pursuing high output activitiesGrab a pair of these if you are looking for an affordable and warm pair of Merino wool bottoms
Rating Categories Artilect Boulder 125 Smartwool Classic T... REI Co-op Midweight... Smartwool Intraknit... Meriwool Merino 250...
Warmth (25%)
5.0
9.0
7.0
7.0
8.0
Breathability (20%)
10.0
7.0
7.0
7.0
6.0
Comfort and Fit (20%)
8.0
8.0
7.0
7.0
7.0
Durability (15%)
6.0
7.0
9.0
8.0
6.0
Drying Speed (10%)
8.0
7.0
7.0
5.0
6.0
Layering Ability (10%)
8.0
7.0
7.0
9.0
6.0
Specs Artilect Boulder 125 Smartwool Classic T... REI Co-op Midweight... Smartwool Intraknit... Meriwool Merino 250...
Material 85% Nuyarn Merino wool, 15% nylon 100% Merino wool 100% polyester 54% Merino wool, 43% polyester, 2% elastane, 1% polyamide 100% Merino wool
Fabric Weight 125 g/m² 250 g/m² Not stated ~200 g/m² 250 g/m²
Weight (size medium) 4.3 oz 8.3 oz 7.4 oz 9.2 oz 7.9 oz
Insulation Weight Lightweight Midweight Midweight Lightweight Midweight
3/4 Boot-Cut Available? Yes Yes No Yes No
Fly? No Yes Yes No Yes
Dryer Safe? No No Yes No No

Our Analysis and Test Results

Most of the magic of the Artilect Boulder 125 leggings comes from the use of its namesake via a 125 g/m² 85%/15% Merino wool/nylon blend called Nuyarn. We were skeptical over some of the claims presented, but our lab and field tests have shown there's something to wool free-spun around a nylon core. This allows the wool filaments to come forward to fully express what makes wool amazing, leaving the nylon core in the background and out of the way to strengthen the fabric itself. What you get is a great warmth-to-weight ratio fabric — this lightweight also means a smooth-feeling legging that breathes amazingly well and dries quickly. We wouldn't baby these leggings on a trip, but be mindful of caring properly for them when you're back in civilization to facilitate keeping them lasting for years to come.

Performance Comparison


artilect boulder 125 long underwear review - perforated fabric up top promotes breathability wrap around the...
Perforated fabric up top promotes breathability wrap around the waist, and waist panels create a slight taper to the top of the leggings.
Credit: Justin Simoni

Warmth


We put the Boulder 125 to the test on a shoulder season backpacking trip into Colorado's high country, wearing them under our top layers on alpine starts and while sleeping in our minimalist open-air bivvies high above treeline. For their svelteness, the amount of warmth the Boulder 125 provides is exceptional, even when we knew we were stretching the abilities of such a lightweight pair of long underwear. We woke up toasty even when we noticed the water in our bottles was icing over.


As a Spring, Summer, and Fall piece, these leggings could be perfect — overheating shouldn't be a problem, especially if you're on the move. You may want to consider a different, heavier-weighted pair of long underwear for colder trips.

artilect boulder 125 long underwear review - these leggings worked admirably as a baselayer while bivvying right...
These leggings worked admirably as a baselayer while bivvying right off the Colorado Trail or high up a mountain ridge during the Spring shoulder season.
Credit: Justin Simoni

Breathability


Using thin, 125 g/m² wool fabric, it's no mystery why these leggings are some of the most breathable long underwear we've ever reviewed: the 85% Merino wool/15% nylon fabric is absolutely sheer in appearance. In fact, you'll even discover small gridded holes — what Artilect calls "eyelets" — in specific areas: the back of the waist and on the gusseted inner leg, allowing even more heat and moisture to escape. Couple this with the wicking nature of Merino wool, and these pants thermoregulate very effectively.


We appreciated these additional more breathable parts as they kept us dry and happy when snoozing in our sleeping bags and saved us from an awkward midnight costume change by headlamp. In the morning, as the temps ramped up on our backpack down, we were thankful to be able to keep the underwear comfortably on until we could find a good place to change.

artilect boulder 125 long underwear review - breathability was excellent while on the go with the artilect.
Breathability was excellent while on the go with the Artilect.
Credit: Justin Simoni

Comfort and Fit


Comfort is high for the Boulder 125. The lightweight Merino wool/nylon blend moves easily with you as you roam around your environment and lofts up higher than its weight alone would have you predict. We didn't experience any bunching up as the cut is more on the fitted side. These tights are stretchy but recover quickly to their normal state. Surprisingly, no additional elastic material has been added to the fabric; it's all from the Nuyarn wool/nylon blend.


We found the additional breathability afforded by the eyelets in the lower waist and gusseted crotch pretty clutch when temps got higher. The flatlock seams are stitched using a very thin thread that keeps chafing and irritation at bay, even though there are more panels to the construction on these leggings than most.

artilect boulder 125 long underwear review - the gusseted crotch helps make these leggings both more durable and...
The gusseted crotch helps make these leggings both more durable and comfortable; the added perforations in the paneling itself facilitates thermoregulation.
Credit: Justin Simoni

Fit does seem to be on the slimmer side. Of note: the manufacturer's measurements are for the wearer and don't reflect the garment's measurement. For example, our pair of size mediums had a waist diameter of 31" but are designed for a waist between 33" and 35" (our tester sizes pants for a 32" waist). If you're used to picking out technical outdoor gear from Europe, get into that mindset when choosing your size. We suggest that if you're on the cusp of a size, go up.

artilect boulder 125 long underwear review - fit is slimmer than some other offerings, but still works for a...
Fit is slimmer than some other offerings, but still works for a variety of body types.
Credit: Justin Simoni

Our main tester is a cycling enthusiast known to haunt the weight room squat rack, and these tights fit acceptably, thanks to the fabric's stretchiness. The elastic waistband measures 1.25" thick and keeps the tights up without feeling too constrictive. Like waist diameter, the inseam length is a little shorter than what we normally expect for a medium: we measured a 28" inseam (Artilect doesn't state an inseam) so if you're especially long-legged, also consider sizing up. Do be mindful when washing the Boulder 125 as the Merino wool could shrink slightly if dried incorrectly. Sizes from XS to XXL are available, but not Short or Long. Finally, there's no fly on these pants. Rather, it sports a two-fabric layer on the front panel.

artilect boulder 125 long underwear review - a slightly loose fit means one can move around without being too...
A slightly loose fit means one can move around without being too constricted, even for cross-the-country cyclists. The length is a little shorter than other pairs of size M we've reviewed (model has 32" inseam length).
Credit: Justin Simoni

Durability


Durability is loosely correlated with the weight and type of fabric being utilized. The lightweight 125 g/m² Merino wool-based fabric in the Boulder 125 will set the realistic ceiling on what you can expect from such a thin fabric: it's just going to be less durable than a heavier fabric. The fabric Artilect utilizes, called Nuyarn, does reinforce the natural fibers by spinning them around a nylon core at a proportion of 85% wool and 15% nylon.


Because the wool is what's exposed, expect some cosmetic wear to happen early on. Fuzzing and pilling of the wool will inevitably happen. In our real-world tests outside on a strenuous backpacking trip, this pilling was incidental, and the leggings retained their integrity showing no tears in the seams or fabric, as well as preserving their stretch and recovery.

Our laboratory abrasion test takes no prisoners, and we saw fabric rips similar to other similarly weighted garments. We would be cautious about wearing these as our only layer in rough, outdoor locales, such as traveling in thick brush or scrambling/rock climbing. Under an outer layer, these tights will perform wonderfully.

artilect boulder 125 long underwear review - the boulder 125s are made of nuyarn: wool spun on a nylon core with...
The Boulder 125s are made of Nuyarn: wool spun on a nylon core with no added elastane.
Credit: Justin Simoni

Since these leggings are made of natural materials, we also stress following the manufacturer's washing instructions to prolong the garment's life. Artilect is fairly strict: wash inside out on the gentle cycle and dry in the shade. If you don't want to commit to babying these while washing, consider a different pair and perhaps a fully synthetic fabric that can take a little more abuse.

Drying Speed


The Boulder 125 are speed demons when it comes to on-the-line drying. This can be explained by the very thin, 125 g/m² NuYarn Merino wool blend fabric, which just doesn't hold onto as much moisture as a heavier fabric. NuYarn is also purported to have a "5x Faster Drying Time," but our on-the-line drying tests don't make sense of this claim. What we can say is that wool/synthetic blends will usually dry faster than a pure 100% Merino wool blend of the same weight, and our own results can corroborate.


We can't talk about drying speed without talking about how to wash and dry the Boulder 125. The manufacturer's recommendation is to wash them inside out, on delicate, with only wool-specific or mild detergent. Drying should only be done on the line (or lying flat) in the shade. We would follow these recommendations to prolong the lifespan of these leggings and protect your investment.

artilect boulder 125 long underwear review - air drying these leggings shouldn't be a problem on trail, but...
Air drying these leggings shouldn't be a problem on trail, but remember to continue to do that once home as well!
Credit: Justin Simoni

Layering Ability


Like most of the long underwear we've tested and reviewed, the Boulder 125 is fairly specialized for working within a layering system. Doubly so for these, as the thin Merino blend didn't get high scores in our lab's harsh durability tests. You probably wouldn't want to wear these without another layer, except for nighttime sleeping bag duty, and for that, they'll work great.


As part of a system, the Boulder 125 performs exquisitely. The thin, 125 g/m² fabric, snug fit, and additional ventilation patterns mean breathability is top-notch. Adding extra layers continues to be comfortable. We mostly layered up with appropriate bottom pieces, like running tights and lightweight mountaineering pants. For additional warmth, you could double the Boulder 125 up with an additional base layer — the Boulder would likely be the next-to-skin layer as the snug fit probably isn't the best to add additional bulk underneath.

artilect boulder 125 long underwear review - the artilect boulder 125 complements best when paired with a high...
The Artilect Boulder 125 complements best when paired with a high performance outer layer like a running tight or mountaineering pant.
Credit: Justin Simoni

Should You Buy the Artilect Boulder 125?


These leggings are uncompromising in providing you with a versatile, warm, durable, and breathable pair of long underwear. For shoulder season and summer adventures, they're one of the best choices for your next outdoor adventure when the temperature starts to dip down. Because they're so light, bring them along as "just in case" insurance and indulge in their comfort.

There's a lot to think about when purchasing a pair of long underwear, not the least of which is the price. The Boulder 125 is not the cheapest pair of long underwear on the market, but with its price comes the quality of the materials used, the sewing, and the cut and design. Regardless, these leggings are an investment. And with an investment comes proper care. If you are up to the task of maintaining these properly, you'll reap the rewards of wearing good-looking, warm, breathable long underwear at an ultralight weight.

artilect boulder 125 long underwear review - these woolies are super comfy both when going full tilt in the...
These woolies are super comfy both when going full tilt in the mountains and while back snoozin' at base camp.
Credit: Justin Simoni

What Other Long Underwear Should You Consider?


If the Artilect Boulder 125 leggings aren't warm enough, look at the Icebreaker BodyfitZone Merino 260 Zone Thermal Leggings, which provide a lot of the same breathability benefits but with thicker, almost 100% Merino wool in key areas. The Smartwool Classic All-Season Merino Bottom are also a great, cozy pair of leggings without being in a totally different class of warmth. For synthetics, seek out the REI Co-op Midweight Bottoms, which are another great synthetic pair of all-season long underwear.

artilect boulder 125 long underwear review - the artilect boulder 125 takes only a small amount of space in the...
The Artilect Boulder 125 takes only a small amount of space in the pack for summer season overnight trips where the weather can be unpredictable.
Credit: Justin Simoni

Justin Simoni
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