Sitka Merino Core Lightweight Half Zip Hunting Shirt is perfect for Mild, Cool, Cold and Extreme Cold climates. It features premium 17.5-micron merino wool spun around a nylon core, creating 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 Half-Zip excels as a versatile base layer across a broad range of conditions and activity levels.