The next-to-skin base layer should be the foundation to your layering system - whether you are climbing Everest, or stalking antelope in Eastern Montana, there is no debating the first step in combatting cold weather conditions. 

Synthetics may be standard issue for military use, though KUIU champions Merino wool over artificial alternatives.

Why? Merino is naturally odor-resistant, thermo regulating, provides insulation while wet, and is ideal in arid climates 👊

Nature provides the solutions 

Further reading via Jason Hairston 📚

Tried and tested by the likes of the FBI, Dutch Special Forces, and exploratory diving teams, Fourth Element takes product development fairly seriously. 

The J2 series was created specifically for a project mapping the Chevé Cave system - the deepest proven freshwater hydrological system in the world (1.5km BSL) - though should be suitable for a Sunday stroll too. 

"Extreme people get extreme results" - via Naval Ravikant

My first Icebreaker field test experience was a 28 day backpacking course with NOLS in 2009, and I have been an evangelist ever since. 99% of the time I am head-to-toe (literally) monobrand 🐏 

Ranging from ultralight to midweight, the offering is super extensive (thanks to VF Corp. backing), and the quality is top notch. Smartwool may offer similar textiles with comparable performance, though Icebreaker delivers on design and fit.