Sitka Merino Core Ltwt Bottom Optifade SubalpineThe new Merino Lightweight Bottom features premium 17.5-micron merino wool spun around a nylon core, which produces a high-performance next-to-skin layer that combines the comfort, warmth, moisture management and natural odor control of merino with the durability and elasticity of nylon. With a high heat-to-weight ratio and excellent breathability, the Merino Lightweight Bottom excels as a versatile base layer across a broad range of conditions and activity levels.85% 120-gram 17.5 Micron Merino / 15% Nylon Core-Spun Blend for natural odor resistance and durability.