How to Choose Base Layers

Ideal for year-round use in traveling, hiking or relaxing after a big day outside, the Icebreaker Siren Sweetheart top is soft and stretchy with an updated fit and fabric that make it even more comfy.
Imported.
View all Icebreaker Women's Base Layer Tops| Best Use | Casual |
|---|---|
| Shirt Type | T-shirt |
| Fabric | 83% merino wool/12% nylon/5% Lycra spandex |
| Moisture Wicking | Yes |
| Underwear Weight | Lightweight |
| Sleeve Length | Long Sleeve |
| Gender | Women's |
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I love this shirt!! I honestly have been wearing it almost every day this winter. Perfect for hiking or just an everyday shirt to keep you warmer. Stylish and comfortable! I ordered XS I'm about 5'4' 115 pounds
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.
The neckline is pretty wide open and the body fits close. I got my usual size medium, and it's very close-fitting though not tight. It feels a bit itchier than the Icebreaker merino 200 oasis crewneck.


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