Helikon-Tex US Level 1 Thermal Layer — Long Underwear
Helikon-Tex
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The Helikon-Tex US Level 1 long underwear is the lower base layer designed for anyone who spends hours outdoors or moving continuously: hunters, static-position shooters and operators working in cold environments. Made from 100% polyester with a weight of 160 g, they fit close to the body without restricting movement and layer cleanly under tactical or trekking trousers without adding bulk.
The technical polyester works through active moisture transport: it draws sweat away from the skin to the outer face of the fabric, where it evaporates, keeping the skin surface dry during intense effort or rapid changes of pace. This mechanism is critical at the base layer, because a damp first layer cancels the thermal insulation of everything worn over it. Unlike cotton, which absorbs and holds moisture, polyester releases it quickly and retains its thermal properties even when wet.
The zip-free construction and absence of hard seams in contact zones eliminate pressure points during movement and reduce the risk of chafing on long marches. This is a deliberate trade-off: a folded-fabric waistband does not offer the adjustability of an elasticated zip closure, but it never creates a hard edge against the skin and will not open unintentionally under load-bearing equipment. For anyone wearing a tactical belt or a plate carrier, the absence of hardware at the waist is a practical advantage.
Key features
- Fabric in 100% polyester with active moisture management: keeps the skin dry during sustained effort and preserves the effectiveness of outer layers.
- Weight of 160 g: a lightweight base layer that does not add to overall load or limit mobility.
- Zip-free construction: no rigid edge at the waist, compatible with tactical belts and load-bearing systems without interference.
- Close fit and low profile: slides under any tactical or trekking trouser without bunching or restricting freedom of movement.
- Available in 7 sizes from XS to 3XL with a waist circumference from 67 cm to 96 cm and a total length from 106 cm to 113 cm.
Specifications
Sizes
TROUSER SIZE GUIDE
The Viper trouser size listed on the site refers to the waist measurement in inches. To find the right size, simply check which waist measurement corresponds to your size. For example, an Italian size 46 corresponds to a 32" waist, so you should select size 32 on the site. You can also choose to measure your own waist and select the corresponding size. If your waist measurement is 90 cm, for instance, you should select the corresponding size in inches, which is 36". Contact us via chat or email with any questions. The size shown on the site corresponds to the waist measurement in inches.
| International | VIPER SIZE (waist in inches) |
Waist in CM | UK | FR | IT | ESP |
|---|---|---|---|---|---|---|
| XXS | 26-28 | 66-71 | 32 | 38 | 42 | 36 |
| XS | 28-30 | 71-76 | 34 | 40 | 44 | 40 |
| S | 30-32 | 76-81 | 36 | 42 | 46 | 44 |
| M | 32-34 | 81-86 | 38 | 44 | 48 | 48 |
| L | 34-36 | 86-91 | 40 | 46 | 50 | 52 |
| XL | 36-38 | 91-96 | 42 | 48 | 52 | 56 |
| XXL - 2XL | 38-40 | 96-101 | 44 | 50 | 54 | 60 |
| XXXL - 3XL | 40-41 | 100-104 | 46 | 52 | 56 | 64 |
| XXXXL - 4XL | 41-43 | 105-109 | 48 | 54 | 58 | 68 |
FOOTWEAR SIZE GUIDE
| TYPE | SIZES | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| EU/IT | 38 | 38.5 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46.5 | 48.5 |
| UK | 5.5 | 6 | 6.5 | 7 | 7.5 | 8 | 8.5 | 10 | 11 | 12 | 13.5 |
| USA | 6 | 6.5 | 7 | 7.5 | 8 | 8.5 | 9 | 10.5 | 11.5 | 12.5 | 14 |
| JP | 24 | 24.5 | 25 | 25.5 | 26 | 26.5 | 27.5 | 28.5 | 29.5 | 30.5 | 31.5 |
| MEX | 4.5 | 5 | 5.5 | 6 | 6.5 | 7 | 7.5 | 9 | 10 | 11 | 12.5 |
| BR | 36 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 46 |
| AU | 5.5 | 6 | 6.5 | 7 | 7.5 | 8 | 8.5 | 10 | 11 | 12 | 13.5 |
Marca
Helikon-Tex
Technical clothing, field equipment and carry systems by Helikon-Tex. It is the most represented brand in the catalogue for outdoor and tactical gear, with over seven hundred product references.
