Helikon-Tex US Level 1 — base layer thermal top

The Helikon-Tex US Level 1 Underwear Top is a long-sleeve base layer designed for those who wear armour, harnesses or combat shirts over it and cannot afford friction, raised seams or sleeves that ride up. Weighing 156 g and built entirely from 100% polyester, it functions as a moisture-management layer against the skin, wicking sweat away to outer layers rather than holding it in.

Flat seams eliminate pressure points that become painful under a plate carrier or vest after hours of use: the difference is not felt in the first twenty minutes — it is felt after a full day of activity. The raglan sleeve cut moves the shoulder seam away from the contact zone with harness straps, maintaining full arm abduction without fabric bunching under the armpit.

Thumb holes at the cuff ends are a detail that changes practical use: they keep the sleeve in place at the wrist when pulling on a glove or lowering an outer sleeve, removing the constant need to straighten the fabric. This comes with a deliberate trade-off: polyester manages sweat well during movement but retains less warmth at rest compared to a merino wool fabric. The US Level 1 is chosen for high-intensity activity in cold months, not as static insulation.

Key points

• Flat seams throughout: no friction points under a vest, plate carrier or harness even after hours of use.
• Raglan sleeve cut: the seam does not fall on the shoulder and does not interfere with overlying straps or shoulder pads.
• Integrated thumb holes: sleeves stay in position when putting on gloves or outer layers, without having to straighten them.
• 100% polyester at 156 g: moves moisture away from the skin during intense activity, maintaining a dry feel.
• Seven sizes available from XS to 3XL, with back length ranging from 70 cm to 82 cm for reliable coverage even on a long torso.