Artilect Boulder 125 Review

Most of the magic of the Artilect Boulder 125 leggings comes from the use of its namesake via a 125 g/m² 85% Merino wool,15% 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. 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

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. The amount of warmth the Boulder 125 provides is exceptional for their svelteness, 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. “When I'm ultralight backpacking in the mountains, I tend to be a weight-weenie,” says Justin Simoni, our lead reviewer. “These are the lightest pair of long underwear I have ever tried, and for their weight, they really did add warmth and comfort day and night.”

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. “These Artilects just don't have enough weight to be useful in the colder, darker months. Then, I reach for something else entirely,” says Simoni. You may want to consider a different, heavier-weighted pair of long underwear for your colder trips.

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, like the back of the waist and on the gusseted inner leg, where they can allow even more heat and moisture to escape. “Those eyelets act almost like the pores on your skin, allowing perspiration an easy way to exit into the air,” says Simoni. 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. They also saved us from the 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. “Sometimes I even forget I have them on underneath my running pants! Whatever is the opposite of 'stuffy' is, these are that,” admits 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; the stretch is 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.

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 inches but are designed for a waist between 33 and 35 inches (our tester sizes pants for a 32-inch waist). If you're used to picking out technical outdoor gear from Europe, get into that mindset when choosing your size. We suggest you go up that if you're on the cusp of a size.

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 inches 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-inch inseam (Artilect doesn't state an inseam), so if you're especially long-legged, consider sizing up. 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.

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 will justo be less durable than a heavier fabric. The fabric Artilect utilizes, called Nuyarn, reinforces the natural fibers by spinning them around a nylon core at a proportion of 85% wool and 15% nylon.

Because the wool is exposed, expect some cosmetic wear 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 and 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.

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 is a speed demon when it comes to drying on the line. This can be explained by the very thin, 125 g/m² Nuyarn Merino wool blend fabric, which doesn't hold 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. We can say that wool-synthetic blends will usually dry faster than a pure 100% Merino wool blend of the same weight, and our results can corroborate.

We can't talk about drying speed without talking about how to wash and dry the Boulder 125. Themanufacturer recommends washingh 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.

Layering Ability

Like most long underwear we've tested and reviewed, the Boulder 125 is fairly specialized for working within a layering system. “These are technical long bottoms,” says our lead tester. 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. “With all the eyelets, you're going to feel half-naked wearing these — you'll definitely need a top layer when out in public!” giggles Simoni.

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 isn't the best to add additional bulk underneath.

Should You Buy the Artilect Boulder 125?

These leggings are uncompromising in providing 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. “These take up little room in my 30L pack, so if I'm doing a summer backpacking route that sees me camping up high, there's no reason I can think of not to bring them for a better night's sleep and a more comfortable morning,” Simoni says.

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. “Just like pretty much all my ultralight equipment, I treat the Artilect Boulders with a little more TLC — especially when it comes to washing day,” says Simoni. If you are up to maintaining these properly, you'll reap the rewards of wearing good-looking, warm, breathable long underwear at an ultralight weight.

What Other Long Underwear Should You Consider?

We also love the cozy Smartwool Classic All-Season Merino Bottom. For synthetics, seek out the REI Co-op Midweight Bottoms, another great synthetic pair of all-season long underwear.