REASONS TO BUY
Fit is true to size
Fabric doesn't retain odor
Great thumb loops
Thick and warm
REASONS TO AVOID
Expensive
Thick fabric lacks breathability
Difficult to layer
Longer drying time
Stio Basis PeakWool Midweight Half Zip - Women's Review
This midweight layer is a solid choice for those seeking warmth during low to moderate output activities thanks to its thicker Merino wool and synthetic blend construction
The Stio Basis PeakWool Midweight Half Zip features one of the thickest midweight constructions that we've tested and includes a longer torso and sleeves along with thumb loops for additional warmth.
Credit: Trish Matheny
By Trish Matheny ⋅ Review Editor ⋅ April 1, 2026
RELATED: The Best Base Layer for Women
Our Verdict
The Stio Basis PeakWool Midweight Half Zip is a high-quality Merino-wool and synthetic blended base layer that features a super-thick 280g/m² midweight construction. For reference, this is more than double the weight of some other layers we tested. The fit is true to size but has a longer length in the torso and sleeves, along with functional and cozy thumb loops for additional coverage. We wish the 1/4 zip neck featured a higher collar for more coverage on the neck, but it's great for offloading some body heat if you work up a sweat. The overall thickness limits its versatility and slows down its drying speed, but we think it's a great layer for sedentary warmth in the cabin, on the chairlift, or on a dog walk during the cold and dark months.
Compare to Similar Products
 This Product
Stio Basis PeakWool Midweight Half Zip - Women's | |||||
|---|---|---|---|---|---|
| Awards |  Favorite Crew for Everyday Use |  Best Synthetic Bang for Your Buck | More Affordable Merino | Best Merino on a Tight Budget | |
| Price | $160 List | $120 List Check Price at REI | $55 List Check REI (on sale!) | $100 List Check Backcountry (on sale!) | $60 List Check Price at Amazon |
Overall Score  |
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| Star Rating | |||||
| Bottom Line | This midweight layer is a solid choice for those seeking warmth during low to moderate output activities thanks to its thicker Merino wool and synthetic blend construction | A lightweight base layer that features supersoft Merino wool along with a thoughtful design and fit | This durable base layer features a soft and stretchy fabric and a slim fit for a variety of activities, all for an affordable price | A lightweight Merino wool base layer crew that prioritizes comfort and breathability with a touch of nylon for increased durability | A durable crew for those who are willing to sacrifice degrees of softness and comfort for a Merino option that can be picked up at a budget price |
| Rating Categories | Stio Basis PeakWool... | Icebreaker Merino 20... | REI Co-op Midweight... | Smartwool Classic Al... | Merino.tech 250 Crew |
| Warmth (25%) | |||||
| Breathability (20%) | |||||
| Comfort and Fit (20%) | |||||
| Durability (15%) | |||||
| Drying Speed (10%) | |||||
| Layering Ability (10%) | |||||
| Specifications | Stio Basis PeakWool... | Icebreaker Merino 20... | REI Co-op Midweight... | Smartwool Classic Al... | Merino.tech 250 Crew |
| Fabric Weight Class | Midweight | Midweight | Midweight | Lightweight | Midweight |
| Material | 56% Merino Wool, 23% TENCEL, 12% Recycled Nylon, 7% Nylon, 2% Spandex | 100% Merino wool | 92% recycled polyester, 8% spandex | Merino jersey: 88% Merino wool, 12% nylon core | 100% Merino wool |
| Fit | Slim fit | Slim fit | Regular fit | Regular fit | True to size |
| Odor Control Fabric | None | Naturally odor resistant | None | Naturally odor resistant | Naturally odor resistant |
| Avaliable Cuts | Crew, Half Zip | Crew, 1/2 zip neck | Crew, 1/2 zip neck | Crew | Crew, 1/4 zip |
| Torso Length | Medium | Medium | Medium | Medium | Medium |
| Thumb Loops | Yes | No | No | No | No |
| UPF Sun Protection | None listed | None listed | 50+ | None listed | 50+ |
| Flat-lock Seams | Yes | Yes | Yes | Yes | Yes |
| Measured Weight (Size Small) | 9.3 oz | 6.3 oz | 7.4 oz | 4.5 oz | 6.5 oz |
Our Analysis and Test Results
The Stio Basis PeakWool Midweight Half Zip is the perfect layer for women looking for maximum warmth and comfort during the coldest months of the year. Credit: Trish Matheny
Likes
One of the first things you notice about the Stio Basis PeakWool is the softness of the fabric. It blends 56% Merino Wool, 23% TENCEL, 12% Recycled Nylon, 7% Nylon, and 2% Spandex, which gives it a good balance of skin feel, stretch, and structure. It feels cozy, a little like being hugged.
If you are looking for a truly warm layer, the PeakWool is one of the best we have tested. You'll immediately feel the 280g/m² fabric weight, which is more than twice as heavy as some of the lightweight options we tested. Our testers love this layer for the coldest days of the year, or for days when you'll be spending long hours outdoors sitting on a chairlift or standing around a winter bonfire. It works fine as a standalone shirt under a puffy on days when you don't feel like pulling on layer after layer to stay warm.
The length throughout the sleeves and torso is also fantastic for women who are after a longer fit to tuck into their ski pants and pull through the sleeves of their jacket. The thumb loops are soft and cozy, and they provide additional coverage to keep your hands warm.
Even though its a thicker wool base layer, the fabric is pretty smooth and easy to layer beneath your favorite down jacket. Credit: Trish Matheny
Dislikes
While Merino wool is typically quite breathable, we found that the overall thickness of this design featured a tightly woven fabric that's great for maximizing warmth but limits the overall breathability. If you wear this top for anything more than a brisk walk, you'll likely sweat it out.
The thickness of the fabric, as well as the longer sleeves and length, requires a super long time to dry both on the body and in the sun. While it does a great job of keeping you warm, it may be too warm for more active wearers. For this reason, we recommend it for low-output activities like riding the chairlift or taking evening walks during the coldest months of winter.
The Stio Basis PeakWool Midweight Half Zip is a thick and cozy primarily Merino wool-blended base layer that features functional thumb loops, a 1/4 zip neck, and longer dimensions that provide additional warmth and coverage. Credit: Trish Matheny
Should You Buy the Stio Basis PeakWool Midweight Half Zip?
The Stio Basis PeakWool Midweight Half Zip is a great choice for ladies who are after maximum warmth for low to moderate output activities. This 280g/m² midweight primarily Merino wool blended layer acts more like a heavyweight option and it feels great next to your skin. Although we wish the collar was higher to provide more neck coverage, we stayed warm enough that this wasn't a big deal most of the time. Although this layer is a bit of an investment, it might be worth the extra dollars for ultimate warmth and coziness during the winter months.
What Other Women's Base Layers Should You Consider?
If you like the sounds of the Stio Basis PeakWool but are interested in something more affordable, check out the Smartwool Classic Thermal Merino 1/4 Zip. The Smartwool isn't as thick nor as durable but it's available for a fraction of the cost. If you're after a more versatile, lightweight base layer that still provides excellent warmth to weight ratio, we recommend the Icebreaker Merino 200 Oasis Crewe. It is 100% merino wool, and is the perfect everyday option to wear under a sweater or hoody.
—Trish Matheny
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