The Polar Vortex Thermal Jacket came to life a few years ago during one of the coldest spells in the Virginia Blue Ridge Mountains. Those who braved the weather needed something to keep out the extreme cold so we developed this. The barrier outside layer keeps water drops out but allows sweat vapor to escape through the directional mesh inside layer. Lycra sleeve cuffs keep out any cold air that tries to find its way up. The high fleecy collar keeps the neck warm, and the single rear zip pocket keeps your phone away from back sweat on long climbs.