There's few things worse than working up a sweat only to be drenched in sweat, especially in cold conditions. Whether you're running or breaking out the nordic skis, the lightweight Kor Stasis Hoody insulates against the cold while letting vapor pass through so pesky heat dissipates. A weather-resistant Pertex Quantum Air outer means a little rain won't leave you high and not-so-dry, while PrimaLoft Active insulation lends the stretch you need for high-octane tempos.