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This product is no longer available, but don't go just yet.


  • Made of soft, nonirritating merino wool with a touch of spandex for stretch, the Icebreaker Siren Sweetheart resists odors naturally
  • Merino wool wicks away moisture, dries quickly and breathes to regulate temperature for outstanding comfort in a variety of conditions
  • With a UPF rating of 50+, fabric offers very good protection from UV light
  • Slim fit
  • Machine washable, line dry or dry flat in shade
  • Please note: this item includes only the Icebreaker Siren Sweetheart top


View all Icebreaker Women's Long Underwear Tops

REI membership


Best Use Multisport
Shirt Style Scoop
Fabric 96% merino wool/4% spandex
Sun-Protective Fabric Yes
Moisture Wicking Yes
Quick Drying Yes
Underwear Weight Lightweight
Sleeve Length Short Sleeve
Gender Women's

Size chart

Sizing notes

Measurements are stated in inches unless otherwise indicated. CHOOSING THE RIGHT SIZE: If your body measurements are midway between two sizes, select the smaller size for a tighter fit or the larger size for a looser fit. If your body measurements result in different sizes, we recommend using your chest measurement for tops and your hip measurement for pants.