Sea to Summit Reactor Fleece THERMOLITE LinerUnlike some pieces of winter gear, the Thermolite Reactor Fleece Liner doesnt go into hibernation in the summer. It works really well as a stand alone sleeping bag in air temperatures down to around 50F 10C. If you have warm base layers, you may even find it comfortable at temperatures lower than this. The only thing you need to be aware of is that moving air will pass through the fleece material easily; so you need to be inside a shelter or use a