This Merlin Titan Outlast jacket features an Outlast, thermal regulating wadded liner. Outlast technology, originally developed for NASA, utilizes phase change materials (PCM) that absorb, store and release heat for optimal thermal comfort. Outlast technology is comparable to ice in a drink; as it changes from solid to liquid, it absorbs heat and cools the drink, keeping that drink at the desired temperature for longer. The technology absorbs heat when you get too hot and releases it when you cool. Unlike a wicking technology Outlast is proactive in temperature and moisture management, rather than reactive.