Thermolite Performer MummyLiner is extremely fast drying, wicking liner with high insulation. Thermolite provides warmth and comfort at the lightest weight, even when wet. Its hollow-core fibers trap air for better insulation. Thermolite dries 20% faster than other insulating fabrics and 50% faster than cotton. It wicks moisture away from the skin to the surface of the fabric where it can evaporate more quickly.