Icebreaker Women's Siren SS Sweetheart Thermal T-Shirt - Black, Small

The Icebreaker Women's Siren SS Sweetheart Thermal T-Shirt is a lightweight merino wool base layer that excels at temperature regulation and moisture management. Crafted from a soft, breathable blend of 83% merino wool, 12% nylon, and 5% LYCRA®, this slim-fit top offers natural odor resistance and all-day comfort for active pursuits or everyday wear. The sweetheart neckline adds a feminine touch, while flatlock seams and offset shoulder seams prevent chafing under pack straps. A drop-tail hem provides extra coverage, and the ZQ-certified merino ensures ethical sourcing. Whether you're hiking, traveling, or hitting the gym, this versatile tee keeps you dry, fresh, and comfortable.

Advantages

The Siren SS Sweetheart is engineered for performance. Its merino wool fabric naturally regulates body temperature, keeping you warm when it's cool and cool when it's warm. The Corespun technology wraps merino fibers around a nylon core for added durability without sacrificing softness. Moisture wicking and fast drying properties keep you dry during high-output activities, while the inherent odor resistance means you can wear it multiple times between washes. The slim fit and sweetheart neckline provide a flattering silhouette, and the lightweight 150 g/m² fabric is ideal for layering or standalone use in mild conditions.

Suitable for

• Hiking and backpacking
• Travel and commuting
• Running and gym workouts
• Everyday casual wear
• Layering under mid-layers in cool weather

Key specifications

• Material: 83% Merino Wool, 12% Nylon, 5% LYCRA®
• Fabric weight: 150 g/m² (Lightweight)
• Fit: Slim
• Neckline: Sweetheart
• Sleeve length: Short sleeve
• Layer type: Base layer
• Odor resistance: Yes
• Moisture wicking: Yes
• Breathability: High
• Temperature regulation: Yes
• Seam construction: Flatlock seams, offset shoulder seams
• Hem style: Drop tail
• Sustainability certification: ZQ Merino
• Care: Machine wash cold, line dry in shade
• Colour: Black
• Size: Small

Recommendations

For optimal performance, wear this thermal t-shirt as a base layer under a mid-layer in cooler conditions or on its own during high-exertion activities. Pair with Icebreaker's merino bottoms for a complete moisture-managing system. Machine wash cold with like colours and line dry in shade to preserve the fabric's natural properties. Avoid fabric softeners and bleach. Due to its odor resistance, you can wear it multiple times between washes, making it an excellent choice for multi-day trips.