Tracksmith - The Downeaster Crew long sleeve Size XS Coffee heather brown This Merino wool long sleeve blend regulates temperature, wicks moisture, and resists odor, even after multiple wears without washing. Downeaster Crew is designed with comfort and versatility in mind, combining the inherent properties of Merino wool in a pragmatic mid-layer silhouette. Hits at mid hip. features a double knit blend of 60% Merino wool and 40% polypropylene. The natural properties of Merino offer warmth, breathability and odor-resistance, while polypropylene improves wicking and insulation. Not only does polypropylene have the lowest thermal conductivity of any fiber, which means it holds onto heat the longest, it’s also hydrophobic, quickly pulling moisture (i.e. sweat) to the surface where it can evaporate, rather than be absorbed into the Merino. The end result is a high-performance top that can be worn as an outer layer on cool days and act as a breathable and temperature-regulating mid layer on the coldest days.