What is that? Social media lit up when Tao Geoghegan Hart wore a prototype of this base layer up and over the Stelvio on his way to winning the 2020 Giro d'Italia. Those conditions highlight where this piece excels: it provides a surprising amount of warmth by pulling moisture away from the body to keep you warm, but the mesh construction means it's never too hot. Great under a jersey for high-intensity riding or those chilly early-season races.