What are you wearing underneath your shirt, cut-and-sew, or jacket?
As it gets colder, what you choose to wear against your skin—something that’s hidden from view—becomes incredibly important.
Beyond just keeping you warm, it needs to absorb and wick away sweat when you’re active. It should also stay odor-free even after it dries, and maintain its fabric texture. Having a piece like that will surely be a lifesaver.
That might sound a bit dramatic or long-winded, but the bottom line is: let's try wearing high-quality merino wool products. I want you to wear them at all times—whether you're enjoying outdoor activities like cycling or hiking, commuting, or just going about your casual, everyday life. If you do, you’re guaranteed a warm and comfortable life without freezing in the cold air.
Of course, there are many types of merino wool products, and we carry plenty of them here at Circles. While it goes without saying that every single one we stock comes highly recommended, I’d like to introduce a few that I wear often or am considering purchasing myself.
ACLIMA
Originating from Norway, ACLIMA is a clothing brand founded in 1939 that focuses exclusively on merino wool products. Since its inception, they have been passionate about researching and developing wool apparel that supports life in harsh natural environments. Every product uses only mulesing-free wool, and they control every step from production to sales at their own factory in Europe to maintain strict quality standards. Their lineup is vast, and every piece is highly functional.
Among ACLIMA’s products, the one I’ve been wearing most lately is the M’s LightWool 140 Undershirt Tee.
LightWool 140
This fabric, known as LightWool, uses 17.5-micron, 100% merino wool extra-fine fibers. With a 140g/m2 weight and a single-jersey knit construction, it’s comfortable enough to wear even in summer.
【ACLIMA】
M’s LightWool 140 Undershirt Tee
PRICE : ¥13,200 (tax included)
COLOR : Black
SIZE : XS, S, M, L, XL
MATERIAL : Merino Wool 100%
Whether worn under a casual shirt like POBS, under a wool mid-layer, or even under a cycling jersey, it’s incredibly versatile for both everyday life and outdoor activities. You might think that because it’s a short-sleeve, I’ll be wearing it less as it gets colder, but it can be layered over long-sleeve base layers, making it a piece you can wear quite frequently throughout the year. I personally love the natural color, though we are only stocking it in black this season. The comfort is, of course, top-notch.
By the way, there is also a long-sleeve model available in the same fabric.
【ACLIMA】
M’s Lightwool 140 Undershirt long sleeve
PRICE : ¥14,300 (tax included)
COLOR : Black, Ranger Green
SIZE : XS, S, M, L, XL
MATERIAL : Merino Wool 100%
As I mentioned, it’s a very light, thin fabric, so even as a long-sleeve, it’s very easy to layer with other garments.
Woolnet Light
WoolNet, ACLIMA's popular product, features a mesh structure made of merino wool. Thanks to its unique construction, it offers better breathability and quick-drying properties than standard merino wool fabric, yet provides excellent heat retention, making it an essential for winter. However, because of that excellent warmth, there were limited times and situations to wear it. But this Woolnet Light, as the name suggests, has a lighter finish, providing moderate warmth and significantly increasing how often you can wear it. It’s useful for three seasons (excluding summer)—and of course, even in mid-summer, it’s highly useful if you're in a reasonably cool place at higher altitudes.
I often used the Lightwool Sports Singlet (which uses Lightwool on the front and this Woolnet Light on the back) during the summer, and it was incredibly comfortable.
I couldn't miss out on the new series released using this Woolnet Light.
【ACLIMA】
M’s Woolnet Light T-Shirts
PRICE : ¥15,400 (tax included)
COLOR : Black
SIZE : XS, S, M, L, XL
MATERIAL : Merino Wool 100%
Naturally, the fabric is 100% merino wool. Furthermore, because it’s a mesh structure, it achieves excellent quick-drying performance without compromising the moisture-wicking and antibacterial properties of merino wool. The feel is soft and stress-free. Also, the short-sleeve T-shirt style allows for much more frequent use when layered with other long-sleeve items. On days when it’s not too brutally cold, you could even wear it as a short-sleeve base layer and regulate your body temperature with arm warmers. Thinking about that, it would also be very useful for high-intensity activities like running.
【ACLIMA】
M’s Woolnet Light Crewneck
PRICE : ¥17,050 (tax included)
COLOR : Black
SIZE : XS, S, M, L, XL
MATERIAL : Merino Wool 100%
Of course, like the Lightwool, there is also a long-sleeve version available. As it’s just as versatile as the short-sleeve version, I’m strongly considering getting both.
HOUDINI
We’ve also had several new arrivals from HOUDINI, not just ACLIMA. Founded in 1993, HOUDINI is a Swedish outdoor brand based on the concept of "CORE COMFORT = The ultimate in comfort." With design engineering rooted in functional beauty and minimalism, their products are repeatedly tested by their development team and ambassadors—who are experts in their sports—and they continue to pursue highly functional and sustainable manufacturing that minimizes environmental impact.
HOUDINI has a wide lineup as well, but I particularly recommend their series that uses Activist TreeMerino™, a blend of Tencel and merino wool.
Activist TreeMerino™
Activist TreeMerino™ is made from 60% ultra-fine 19.3µm merino wool and 40% Tencel. It features excellent breathability and quick-drying properties, providing thermal regulation that keeps you cool when it's hot and warm when it's cold. Also, because Tencel is a fiber that feels soft against the skin, you can experience a level of flexible comfort that wasn't possible with previous merino wool products. It's so soft that even those with sensitive skin who usually dislike wool won't feel any itchiness. In addition, it features the natural antibacterial, odor-resistant, and insulating properties of merino wool. Oh, one more thing: Tencel also helps prevent static electricity. Dealing with static shocks in winter is a real headache, after all.
【HOUDINI】
M’s Activist Tee
PRICE : ¥12,100 (tax included)
COLOR : Mother Of Greens, True Black
SIZE : XS, S, M, L, XL
MATERIAL : Merino wool 60%, Lyocell Tencel® 40%
A highly functional T-shirt using Activist TreeMerino™
With a regular fit design, it’s perfect for everything from outdoor activities to daily wear, and can be used all year round, regardless of the season.
【HOUDINI】
M’s Activist Turtleneck
PRICE : ¥18,700 (tax included)
COLOR : Mother Of Greens, True Black
SIZE : XS, S, M, L, XL
MATERIAL : Merino wool 60%, Lyocell Tencel® 40%
Designed in pursuit of excellent versatility and comfort, it’s perfect for daily wear. It works great as a base layer for cycling and hiking, but also shines in winter sports like skiing and snowboarding.
As it gets colder, I often layer it over a short-sleeve merino wool T-shirt and then wear a shirt over that. I wear it quite frequently as my casual long-sleeve top.
This season, I’ve chosen the Mother Of Greens and True Black colors.
I really have so many more items I’d love to introduce, but this time I’ve highlighted items that you can start wearing immediately and continue to wear until next spring. If you're interested in other ACLIMA and HOUDINI products, check them out here!!!
