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40g (Size M)
- Introduction
- Ultralight Alpha Sleeves
- Product story
- Our take on Active Insulation
- Product voice
- Design notes: Light Alpha Sleeves
- Layering
- Form and function
- Thermal comparison
- Fast-drying
- Details
- Quick Layering
- Super compact and lightweight
- Upcycled from surplus materials
- Review
- Material
- Polartec Alpha Direct
- Size guide
- Notes before use
- Shedding
- Instructions
- Care instructions
- Repair
Introduction
Ultralight Alpha Sleeves
The Light Alpha Sleeves is made of Polartec Alpha Direct, a material that balances breathability and insulation very well. We designed it so that you can regulate your body temperature by removing or putting on the sleeves, making it ideal for UL hiking, fast packing, and trail running.
Its soft and lightweight texture provides maximum comfort while keeping your arm movement unrestricted. It pairs well with sleeveless or short-sleeve base layers or our mid-layer products such as the Alpha Vest or Alpha Haramaki.
To avoid throwing away surplus materials, The Light Alpha Sleeves are made from upcycling Light Alpha Tights scraps.
Light Alpha Sleeves Features
- Excellent balance of breathability and insulation with Polartec Alpha Direct
- Lightweight and compact
- Draw cord for quick adjustments
- Easy Layering while on the move
- Maintains insulation even when wet
- Thumb holes
- Perfect with our Alpha Vest or Alpha Haramaki
Due to the nature of the material, friction and frequent washing may cause shedding.
*For more detailed information, please refer to Instructions.
Product story
Our take on Active Insulation
We had a project to make a product from surplus Polartec Alpha Direct materials, which led to the development of the Light Alpha Sleeves.
I only occasionally use arm sleeves, and when I do, I opt to use traditional compression type arm sleeves, primarily to help arm fatigue, UV protection and to add a bit of insulation. However, traditional arm sleeves can be somewhat inconvenient to put on/put off. It is even worse when you have a watch on. With that in mind, traditional arm sleeves weren’t a very appealing piece of equipment to me.
When I first got my hands on the prototype for our Alpha Direct Arm sleeves, I found it interesting as a piece of lightweight insulation tool but had doubts whether this would be accepted in the market, since it was so different from traditional arm sleeves.
My perception immediately changed after testing them. I often trail run, and in temperatures around 10 degrees, I sometimes venture out with just a base layer. However, to be prepared for the unexpected, I’ve been making sure to take lightweight mid-layers like the Alpha Vest or Alpha Haramaki as backup.
Traditional long sleeve mid-layers are usually heavier and inconvenient to put on/take off, making it difficult to adjust layering while on the move.
Takahiro Watanabe, wearing the Black color.
The Alpha Direct arm sleeves are easy to put on and provide you with insulation exactly where you need it. By leaving the armpits open, it allows you to maintain warmth without overheating. Quickly roll them down if it gets too hot. The lightweight design allows for all-day comfort and even when combined with the Alpha Vest, they’re significantly lighter than long sleeved mid-layers.
During a summer trip to the Northern Alps in Japan, I left my sleeping bag behind and took an Alpha Vest, Light Alpha Arm Sleeves, Light Alpha Tights and UL All-weather Pants. Even without a sleeping bag, I was able to stay warm in my tent in 10-degree temperatures at night.
In single-digit temperature glaciers of the European Alps, I wore nothing but a DF Mesh Merino base layer, paired with the Alpha Vest and Light Alpha Arm Sleeves while hiking. Not only was I able to stay warm, I never overheated even when the sun was shining in mid-day.
Our founding father, Akira Natsume and the development team refined the prototype, prioritizing easy one-handed adjustments and anti-slip features. Despite its simplicity, the Light Alpha Sleeves carries unlimited layering possibilities, making them an exciting choice for aggressive and active hikers.
Product voice
Design notes: Light Alpha Sleeves
Yamatomichi founder Akira Natsume and product development lead Takahiro Watanabe share the story behind our new Light Alpha Sleeves, highlighting their key features and performance—backed by insights from real-world field testing.
Layering
Alpha Vest & Alpha Haramaki
We recommend the Light Alpha Sleeves with our Alpha Vest or the Alpha Haramaki. Adjust the level of insulation you want freely while on the move. The Light Alpha Arm sleeves are so light, you can roll it down to your wrists when hot, and not feel the weight.
Oji Sonoda 176cm-65kg
Light Alpha Sleeves (Size M / Glacier White)
100% Light Merino Pocket T-shirt (Size M / Jay Blue 2024)
Light 5-Pocket Shorts (Size L / Purple Haze 2024)
Base layer & Trail shirts
In situations where a short-sleeve or sleeveless base layer alone leaves you feeling cold, but adding a mid-layer makes you too warm, the highly breathable Light Alpha Sleeves is the perfect solution.
Also, our short-sleeve trail shirts act as an effective windbreaker, creating a layer to retain body heat from wind, allowing you to stay active even in colder temperatures.
Kaori Kobayashi 170cm-53kg
Light Alpha Sleeves (Size S / Light Gray)
DF Mesh Merino Sleeveless (Size Women L / Slate Blue 2023)
5-Pocket Shorts (Size L / Woodrose 2023)
Tomohiro Kobayashi 181cm-72kg
Light Alpha sleeves (Size M / Black)
Bamboo Short Sleeve Shirt (Size Men XL / Indigo 2023)
5-Pocket Shorts (Size Men L / Glacier White)
Form and function
Thermal comparison
Although it is not as warm as 1000 fill power down, the slightly thick Polartec Alpha Direct (136g/m2) is one of the best insulators available. The Alpha Direct can be used not only in action but also when resting, always keeping you warm.
The chart compares the 1000 fill power down and other insulators used in thermal clothes on the market:
- Heat retention is measured by JIS L 1096 A method, in Yamatomichi in-house test. The heat insulation property is measured by the amount of energy consumed by the heat-generating element to maintain its temperature.
The maximum value is 100%. - The values of Polartec and Primaloft fabrics are the manufacturers’ catalog specs. Other fabrics’ values are measured by Yamatomichi. 1000 fill power down includes its 7 denier nylon outer and lining.
Fast-drying
It offers excellent quick-drying performance—whether it gets wet during a hike or after washing, it dries in no time. Even when damp, it still retains a good level of insulation.
The chart compares the fast-drying performance of middle layer products*. It is shown that Alpha Direct is not as fast-dry as the extremely fast-drying Shadow Rip (UL Shirt), but the moisture content after spin-dry is much lower than that of wool and other fabrics, and even when wet, it dries quickly if lightly wrung out or worn for some time:
*Tested by Yamatomichi. Compared the difference of the water content after completely wet and 15 minutes of spin-dry. The larger the value, the higher the moisture content, meaning slower drying.
Details
The upper opening is equipped with an elastic stretch cord for quick adjustments.
The thumb holes not only prevent the sleeves from rolling up but also provide moderate insulation to the hands.
Rubber lining on the inner side of the opening for extra grip.
Quick Layering
You can quickly adjust your layering to your body’s needs by pulling the Sleeves up when cold and lowering it to your wrists when hot.
Super compact and lightweight
The Light Alpha Sleeves are extremely lightweight, weighing only 37g in Size M, means you can carry it with you at all times without feeling weighed down.
Upcycled from surplus materials
To avoid throwing away surplus materials, The Light Alpha Sleeves is made from upcycling Light Alpha Tights scraps.
This is the cutting diagram for Light Alpha Sleeves and Light Alpha Tights. It’s worth noting that Light Alpha Sleeves are created from the excess fabric that would typically be discarded during the production of Light Alpha Tights.
Review
Here’s how hikers are using the Light Alpha Sleeves out on the trail—along with their honest impressions and what they’ve come to love through real-world use.
I’ve been using the Light Alpha Sleeves nonstop since the summer—on both regular hikes and tough multi-day races like VOLCANO72 and STS.
Even in summer, ridgelines got cold at night, and the sleeves provided enough warmth on their own in windy conditions. In rain, I wore a UL All-weather Jacket over them. Normally, a shell over bare arms feels cold and clammy, but with the open-knit sleeves underneath, I stayed warm and avoided hypothermia.
One of their biggest advantages is how easy they are to put on or take off without removing your pack—super handy during races.
When camping around 1000m, I don’t even pitch a shelter. I nap wrapped in a bivy with the sleeves on, and for longer rests I add the Light Alpha Vest, Jacket, and Tights. The fabric is so soft I even use them like pajamas.
I mostly wear them dry (they're that comfortable!), but since they’re synthetic, they still perform when wet and dry quickly, so I can run again right away. The convenience and versatility mean I keep reaching for them.
Can’t wait to see how they’ll come in handy through fall and winter.
(And honestly, I’d love a version that goes up to the shoulders—perfect for sleeveless runners like me!)
TJAR2024
Nickname: Dustin
A self-proclaimed “indoorsy type who can move” with a deep love for games, anime, and manga. He’d honestly rather not leave the house—but hiking gives him just enough outdoor time to avoid full-blown hermit status.
After years of working abroad, he gained some weight and reluctantly started running to stay healthy (and to justify his love of sweets and beer). One thing led to another… and now he’s walked the length of Japan four times.
2018 – TJAR 2018 (approx. 415 km)
2019 – KLTR 2019 (approx. 400 km)
2020 – TJAR 2020 (approx. 415 km)
2022 – KLTR 2022 (approx. 400 km)
2023 – VOLCANO72 (approx. 250 km)
2023 – STS (approx. 450 km)
2024 – TJAR 2024 (approx. 415 km)
In late July, I wore the Light Alpha Sleeves during a 2-day hike in the Southern Alps, while camping at the Kumanodaira Hut tent site. Even though the nighttime temperatures didn’t drop much, I stayed comfortable until morning with just a bivy, Alpha Vest, and the UL All-weather Coat over the sleeves—no sleeping bag needed.
They’re perfect for those slightly chilly moments before sunrise or when you're hanging around camp—not cold enough for a full long sleeve, but just enough to want something extra. The breathability is great too—heat doesn’t build up while moving, and if you get warm, you can just pull them down to your wrists or take them off. And if the wind picks up, throwing on a wind shell easily traps warmth.
The soft Alpha Direct fabric doesn’t feel tight on the arms, so it’s really comfortable when resting. Lightweight and compact, the sleeves tuck easily into a pocket or sacoche. In summer, I often pair them with a DF Mesh Merino Sleeveless or Alpha Vest—they’re a great tool for fine-tuning comfort and temperature on the trail.
Trail runner
With 12 years of mountaineering experience, Ayako works in Tokyo during the week and escapes to the mountains on weekends. She enjoys a wide range of activities throughout the year—from day hikes and fastpacking to alpine routes, stream climbing, and deep winter mountaineering—spending over 100 days a year in the mountains.
A good beer gives her a boost, and she has a special talent for falling asleep just about anywhere.
Material
Polartec Alpha Direct
Conventional natural down and synthetic insulators tend to contain body moisture within the clothes and as a result, can be quite stuffy. Polartec Alpha Direct, on the other hand, is so air-permeable that it can be worn even during a high level of physical activity.
Alpha Direct is also treated by Polygiene odor control which safely reduces the microorganisms and bacteria by small amounts of silver ions, achieving antibacterial and deodorizing function that well exceeds the lifespan of ordinary garments.
It is like a fleece with longer puffy hairs.
Size guide
Product dimensions
Unit：cm
| Size | S | M |
|---|---|---|
| Length | 46 | 54 |
| Bicep Circumference | 12.5 | 14.5 |
| Sleeve Opening | 8 | 9 |
Choosing a size
- Size M is intended for men, and size S is intended for women.
- If you’re unsure about sizing, please refer to the “Upper Arm Width” mentioned above. Measure the circumference of the widest part of your upper arm (maximum upper arm circumference), and divide that number by 2 to get the upper arm width. For example, if the maximum upper arm circumference is 28 cm, 28 ÷ 2 = 14 cm, and size M is recommended.
Notes before use
Shedding
While lightweight and warm, due to the structure where the lofted fibers are attached to the mesh fabric, hair shedding may occur with use and washing due to wear.
Used 3 seasons
New
Instructions
Care instructions
- Machine wash, below at 30°C, Use neutral detergent.
- Wash separately or use a laundry net bag.
- Do not bleach. Do not use fabric softener.
- Dry flat in the shade to prevent stretching under its own weight.
- When using a dryer, use a low-temperature setting (60°C or lower).
- Do not dry-clean.
- Do not iron.
- If fluff is noticeable at the time of purchase, please wash once.
Care instruction page
For more detailed washing, drying and water repellent care instructions, visit our SUPPORT Page. With proper care you can prolong the funtionality of the product.
Payment
- We only accept payment by credit card. We currently do not accept payment via bank transfer from overseas accounts.
- We accept the following Credit Cards: Visa, Master, American Express, and JCB.
- To download your receipt, please click the link included in the Dispatch Notice, which we will send by email as soon as the items are dispatched.
- Bank transfer is only availble for those that own a Japanese bank account.
Delivery
- Order Confirmation will be sent after the order.
- The items will be dispatched within 3 days after the payment is confirmed.
- The dispatch notice will be sent by email as soon as the items are dispatched.
- The delivery may be delayed by unforeseeable reasons such as natural disasters and other logistics issues. We appreciate your patience and understanding.
- We cannot ship multiple orders in one package due to how our delivery system is currently set up.
- We will ship to regions in North America, Oceania, and Europe (excluding Russia) via DHL. For regions in Asia, the Middle East, Central and South America, Africa, and Russia, we use EMS (International Express Mail Service) for shipping.
- Shipping fees and delivery times vary depending on the shipping destination as well as the size and weight of the items.
Size exchange
- Overseas customers who need to change the size of their order, should note that the time needed for shipping will vary greatly depending on your country of residence.
- We only accept exchanges when the item is unused (except for fitting).
- If you wish to exchange the size of the item, please contact us within seven days of receiving your order.
- Exchanges can only be made for the same color in a different size.
- If the size you wish is out of stock, we will suggest a different color.
- If the product is out of stock, we may simply have to ship the item back to you.
- All shipping costs to be carried by the customer.
- We will only send the exchanged item to you, upon receipt of return shipping cost via PayPal.
- Please be aware that some countries charge customs duties depending on the price of the item.
- We are unable to answer any questions on local customs. Please contact your local customs bureau.
Repair
We accept repairs for all of our Yamatomichi products. For inquiries on repair services including patching the holes, repairing with extra components, or fixing the items damaged over time, please feel free to contact us from the “Repair” section of the SUPPORT page.