Water- and vapor-impermeable sleeping bag liner.

The VaporBarrierLiner Hot Sac VBL from Western Mountaineering is a must when using a down sleeping bag for long periods in low sub-zero temperatures. It prevents body moisture from getting into the insulating layer. This vapor barrier prevents evaporated body moisture from entering the down layer and condensing there at the dew point. Without it, the insulating capacity of the sleeping bag is strongly reduced during long periods of use. The inlet also provides additional insulation and can be used as an emergency bivy sack. Ideal for long winter adventures in very cold areas. The Hot Sac VBL is not so important for weekend tours with drying facilities. Attention: Color varies