Perfect for deep winter adventures. - Western Mountaineering Hotsac VBL Sleeping Bag Liner

An absolutely necessary piece of equipment in a sleeping system for sub-zero temps. Moisture management is crucial for comfort and safety on any trip more than a day or two long at freezing temps. Keeping insulation dry is very important. The WM vbl is nicely made to fit their bags and adds considerable warmth and insulation protection from body moisture. I have used mine for several seasons now and is holding up great.