Aerogel is an innovative insulation material that we use inside our warmest shell boot, the Skare Expedition. Millions of air pockets form a thermal blockade, locking out the cold and keeping the warmth inside, thus making it a fantastic insulator. PrimaLoft® Gold Insulation Aerogel retains an average of 96% of its original thermal performance when used by active feet, which is perfect for our insoles.