The Reactor Fleece Liner built from hollow-core ThermoliteA(R) Pro fibers used in&nb... The Reactor Fleece Liner built from hollow-core ThermoliteA(R) Pro fibers used in a grid-pattern to deliver our warmest sleeping bag liner and the core of any quality cold weather sleep system. You can regulate your temperature using the shoulder zippers and drawcord footbox, which also align perfectly with the Free Flow-Zip system of Sea to Summit sleeping bags. The versatile Reactor Fleece Liner delivers comfort across multiple seasons or can even be used as a stand-alone sleeping bag in warm weather. Additionally, the drawcord footbox offers plenty of ventilation and the versatility of walking around camp while still wearing your liner if needed. Features Thermal boost to retain heat and warmth, as the core of your sleep system the Reactor liner extends the performance of your sleeping bag and sleeping mat in the coldest of conditions Hollow-core ThermoliteA(R) EcoMade fibers are used in a grid-pattern fleece for maximum warmth retention Drawcord footbox can be opened or closed for optimal comfort and integrates perfectly with the footbox of our Free-Flow Zip system in select Sea to Summit sleeping bags HeiQ Fresh odor control technology helps keep the liner fresh even after extended use A mummy shape designed for maximum thermal efficiency and includes shoulder zippers and footbox drawcord for additional temperature regulation Sea to Summit Guarantee is offered for the Lifetime of this product