The Thermolite Fleece Liner is the warmest of our Reactor series and can be used to extend the warmth of your sleeping bag, or can also double as a stand alone summer bag. The Thermolite Fleece is incredibly warm for its weight, and we have given this fabric a brushed finish for extra comfort. The quarter zip makes it easier to get in and out of, and panelled hood can be drawn in when maximum warmth is required.