Just when you thought Merino wool was the ultimate in next-to-skin performance wear, along comes the latest beast du jour — the Yak. And, Jottnar is delivering something special with the Uller Yak wool base layer.

Jottnar Uller Zip Base Layer Features:

  • Made from blended polyester and Yak wool (67/33 mix)
  • Flat lock seams
  • Locking YKK zippers
  • Single chest pocket
  • Drop hem for added coverage
  • Athletic fit
  • MSRP: ~$130 US

Jottnar Uller Base Layer

No Old-school Yakety Yak Stuff Here

Natural fibers have long been the fabric of choice for warmth, breathability and performance. As a long-time lover of all things Merino, it took about a second to recognize the awesomeness of yak wool. Lets review a few things about yak versus merino wool:

  • Yaks are naturally built to handle harsher environments (the best yak wool is harvested from animals living at 15,000 ft.)
  • Yak wool is warmer and more breathable
  • Yak wool is softer to the touch
  • Yak wool is more static resistant
  • Yak wool is certainly more expensive than merino (had to be a catch)

So, I know you’re asking, “how is yak wool harvested?” Well, the best video I’ve found is this one from a competitor. Essentially, every spring they harvest the winter coat and then that wool is transformed into yarn to be used in fabric. US-based harvesters I’ve seen will comb the coat to get the best fibers. It’s almost like a yak spa experience.

With a 67% polyester and 33% Yak wool blend, the Uller is soft.

With a 67% polyester and 33% Yak wool blend, the Uller is soft.

Since Yaks are at home in the highest altitude regions on earth, it make sense that their wool is also well-suited for high-altitude adventures. Knowing this, Jottnar has gone with the finest-quality Yak wool for their Uller Base Layer and it stands out from the crowd.

Founded in 2013, Jottnar is a UK-based apparel manufacturer specializing in mountaineering gear. Their lineup is limited, but each garment utilizes the highest-quality materials from partners such as PolarTec, DownTek and more. As such, the Uller Base Layer fits right into the mix as a go-to top for flexible comfort in the mountains.

Upon arrival, the challenge was to see how many days the Uller could be worn without washing. With natural anti-stink properties, the expectation was at least 7 days if not more. Since the fabric is so comfortable, it wasn’t hard to imagine wearing it consistently for many consecutive days. As mentioned, I’m a noted Merino snob, but this Yak stuff just might win me over for its luxuriously-soft feel and real-world performance. So, the Uller went with me to the office, around town, on the slopes and even running. Only after about 7 days of use did it start to exhibit some body odor — that’s pretty good.

After a good run, it was damp, but dried in a jiffy.

After a good run, it was damp, but dried in a jiffy.

I’d call this a mid to heavyweight base layer. The fabric is more inline with a midweight piece, but its warmth is on par with heavyweight layers. That said, it breathes so well that I wouldn’t compare it with more traditional, stuffy or thick base layers — no way. Yak wool does retain warmth, but not at the expense of breathability. Honestly, it’s downright magical in that regard. On the slopes, I would wear the Uller, Rab Microlight Vest and the Patagonia Untracked Jacket and be just fine for resort skiing in the upper 20’s (Fahrenheit). Anything colder and I’d like a little extra in the sleeves, but only on the chairlift ride up.

The tight knit fabric does also block a little more wind than your typical base layer and serves as a great running top for cooler temperatures. I ran with it in 35-45-degree temps with much success. It breathes well under heavy use and maintains its structure when wet (unlike some Merino tops I have). And, it only takes a short time to dry out after use (while worn or hung up).

The fit is excellent as I went with the size large for my 5’11” 175 lb. body. I have pretty normal proportions and the sleeve length was perfect as was the hem. The only areas where I’d like to see some tweaking is in the collar diameter (could be tighter) and adding thumb ports to the sleeves. All zipping is done via quality YKK zippers and everything features flat lock seams for a chaff-free experience.

It does say to wash the Uller in delicate/wool cycle and line dry. Heaven knows I’m going to have a heck of a time honoring that 100% of the time. I will say that a run with a normal load in a front-load washer and dryer yielded no shrinkage. I’m going to try and be better about it, but with our houseful, there’s just no guarantees.

The Good

  • Awesome Yak wool blend is amazingly-soft
  • Luxurious feel
  • Breathability and warmth is stellar
  • Dries quickly and doesn’t retain much body odor
  • Flatlock seams, YKK zippers and drop hem show quality

The Bad

  • A little hard to get outside the UK
  • Thumb loops and tighter collar would be nice
  • Washing restrictions are always challenging

The Bottom Line: Jottnar Uller

I had no idea just how awesome Yak wool would be until the Uller arrived. After repeated use in a variety of conditions, there’s no doubt this piece stays fresh longer and maintains warmth in a wide variety of conditions.

Buy Now: Available at Jottnar.com


About Author

A native of the Pacific Northwest, Jason quickly developed a love for the outdoors and a thing for mountains. That infatuation continues as he founded this site in 1999 -- sharing his love of road biking, mountain biking, trail running and skiing. That passion is channeled into every article or gear review he writes. Utah's Wasatch Mountains are his playground.

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