Built for changing conditions.
Shop HikingFavorite icebreaker cut
"Love the neckline and cut of this top but definitely size up! So comfy, slightly stretchy, little more durable than some of the super lightweight fabrics."
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A soft and stretchy women’s T-shirt for everyday comfort, the Merino 150 Siren Long Sleeve Sweetheart features our corespun fabric that’s naturally odour resistant and soft next to your skin.
Good for:

83% Merino Wool, 12% Polyamide, 5% Elastane Exclusive Of Decoration
Machine Wash Warm. Wash Inside Out With Like Colors. Do Not Use Softeners. Fasten All Closures To Wash And Dry. Do Not Bleach. Do Not Tumble Dry. Line Dry In Shade. Warm Iron. Do Not Iron Print, Trims And Accessories. Do Not Dry Clean.
Model measurements
Height: 179cm / 5'10". Waist: 62cm / 24". Anya is wearing size S.
Key product measurements
Height: 61.5cm (Based on size S); Width:41.5cm (bottom opening width, size S)
Fit
Slim
The Siren is a lightweight next-to-skin layer. It’s crafted from 150gm merino jersey corespun fabric that’s lighter than most other fabrics we use, and is made with a snug, slim fit that works perfectly as a cosy piece beneath your other layers. Our Siren tees fit tighter than other tees in our range, just size up if you like a looser fit.
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Merino wool neutralizes unpleasant odors by absorbing odour molecules into its fibers, making them less detectable by the human nose.
Merino fibers efficiently manage moisture, absorbing it from your skin and releasing it into the atmosphere. It can absorb up to 35% of its weight in water without feeling wet.
icebreaker merino wool garments undergo special anti-shrinkage treatment, helping to resist deformation and pilling.
The thermo-regulation properties of merino wool adapt to your body and external conditions, so you can stay warm in the cold and cool in the heat.
Overall rating: 4.5946903 / 5 from 565 reviews.
This long sleeve top is praised for its flattering neckline, excellent quality, and chic appearance. Customers appreciate the soft and comfortable feel, though some find the fabric thin and see-through. The fit is generally true to size, but opinions on sizing vary.
Review topics: ["fit","size","delivery","price","weight","quality","feel","problem","looks","material","top","shirt","layer","fabric","wear","base layer","neck","warmth","sleeves","colour","style","comfort","weather","neckline","winter","arms","stretch","icebreaker","shape","collar"].
"Love the neckline and cut of this top but definitely size up! So comfy, slightly stretchy, little more durable than some of the super lightweight fabrics."
— Melissa (5/5)
"For years I wore uniqlo heat tech shirts, but those would get sweaty and stretch out over time, and I would get too hot in them. This shirt is much nicer on the skin as it never made me sweaty and stays fresh for much longer. I lost my shirt and was devestated—and have since bought a new one. I like that the cut of these shirts are low enough that they’re usually not visible underneath other items, and if I do end up taking a layer off I think the neckline is really beautiful and flattering. I do wish the shirts were a bit longer so they could stay tucked in better. I bought a size small (my usual size, with a chest size of 34b) and it fits well, fitted without being tight."
— Lucia S. (5/5)
"Perfect breathable layer for my hike"
— Vp (5/5)
"Great base layer in charcoal. Grey is a little sheer but fine if you wear with a bra underneath. Hugs all the right places."
— Mark (5/5)
"Nice top but I do not like it as much as I like the crew neck."
— LORIE R. (4/5)
"Perfect for base layering under sweaters with low or wide necklines. No visible logo/brand name, which I prefer."
— Alaina M. (5/5)
"Comfortable, snug, base layer. Very happy with it."
— Margaret R. (5/5)
"Perfect fit and weight"
— Julie G. (5/5)
"Superbe!"
— Lisette L. (5/5)
"I was disappointed when this arrived and I realised that I had bought a non 100% wool product. However, I have worn and been won over as it has none of the drawbacks of other mixed products I have worn. Very comfortable and flattering fit. I would not buy a mixed product again (except by mistake) but I am very happy with this top."
— Jean (5/5)
Use the chart below to determine your size. If you’re between two sizes, order the smaller size for a tighter fit or the larger size for a looser fit. If your measurements for chest and waist correspond to two different sizes, order the size indicated by your chest measurement for tops and your hip measurement for pants.
| XS | S | M | L | XL | |
|---|---|---|---|---|---|
| Bust | 30-32 | 32-34 | 34-37 | 37-40 | 40-42 |
| Arm length | 30.25-30.5 | 30.5-30.75 | 30.75-31 | 31-31.25 | 31.25-31.5 |
| Waist | 24-26 | 26-28 | 28-30 | 30-32 | 32-35 |
| Hips | 34-36 | 36-38 | 38-40 | 40-42 | 42-44 |
| XS | S | M | L | XL | |
|---|---|---|---|---|---|
| Bust | 76-82 | 82-88 | 88-94 | 94-100 | 100-107 |
| Arm length | 77-77.5 | 77.5-78 | 78-78.5 | 78.5-79 | 79-79.5 |
| Waist | 58-64 | 64-70 | 70-76 | 76-82 | 82-89 |
| Hips | 84-90 | 90-96 | 96-102 | 102-107 | 107-113 |
Our three different fits - slim, regular, and relaxed - ensure that when worn together, layers move and breathe like a single garment.
Find the size that fits you best based on people just like you.

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