The Seirus Heatwave Skull Liner uses Seirus’ dual-stage heating system to maximize the amount of warmth a liner can generate. The reflective poly-nylon lining helps you retain up to 20% more body heat while kinetic energy from the wicking process is harnessed to provide an additional 4-5 degree increase in warmth. On those days when other liners aren’t enough, slip the Seirus Heatwave Skull Liner on under your helmet and ride through the frigid temps in comfort.