The Smartwool Women's Merino 250 Base Layer Top is a highly rated synthetic base layer top made from merino wool. Merino wool is known for its excellent temperature regulation and moisture-wicking properties. This base layer top offers warmth, breathability, and odor resistance. It is designed with flatlock seams to prevent chafing and a slim fit for easy layering. The Smartwool Women's Merino 250 Base Layer Top is praised for its softness, durability, and performance.