Men's Thermal Base Layer Bottoms SF038/SF033/SF039/SF043/SF044/SF040

Meet the Beneunder Thermal Base Layer Series — built to combat the true discomfort of fall and winter: moisture-induced chill.
This collection uses next-generation moisture-heating fibers, rapid-dry structures, and dual-layer thermal knits to keep your core warm, dry, and breathable through changing temperatures and activity levels.

The HydroHeat line features moisture-activated fibers that boost warmth by up to 8 °C*, helping prevent the cold-cling sensation caused by trapped sweat.
The WarmKnit line uses a dual-layer hollow-core structure that locks in heat while blocking external cold air.

Engineered for hikers, commuters, and anyone who needs stable warmth without overheating or dampness.

Highlights

• Moisture-Heating Tech – Converts sweat into thermal energy, increasing temperature by up to 8 °C* and reducing “wet-cold” sensations.
• Instant Dry-Touch – Rapid moisture-transfer channels move sweat away from the skin for 24-hour comfort.
• Dual-Layer WarmKnit Structure – Inner hollow fibers trap insulated air; outer knit blocks cold drafts.
• Touch-Warm Fabric – Heat-responsive yarns warm instantly on contact, keeping warmth steady even in low temperatures.
• Breathable Warmth – Maintains airflow while retaining heat, preventing stuffiness during activity.
• Soft-Touch & Stretchy – Smooth, flexible knit provides 360° movement for layering or standalone wear.
• Long-Lasting Comfort – Anti-pilling and anti-static treatments ensure durability through repeated washes.