Hot Sac Vapor Barrier Liner Western Mountaineering

The Western Mountaineering Hot Sac VBL is a Vapor Barrier Liner intended as a cold weather sleeping bag accessory.

The VBL works in two ways.

First, the non-breathable coated ripstop nylon prevents evaporative heat loss.

Second, the reflective finish of the coating bounces heat back towards the body.

When used at sub-zero temps, the Hot Sac adds a measure of warmth by keeping your insulation dry and reflecting heat.

At just 4.5 ounces, the Hot Sac VBL can easily fit into your day pack for use as a super lightweight emergency bivy.